Cell construct for cell transplantation and cell aggregate for cell transplantation

ABSTRACT

An object of the present invention is to provide a cell construct for cell transplantation capable of having a thickness suitable for cell transplantation, preventing the necrosis of transplanted cells, and forming blood vessels in the transplantation site after transplantation. The present invention provides a cell construct for cell transplantation which comprises polymer blocks having biocompatibility and cells of at least one type, wherein the plural polymer blocks are arranged in spaces between the plural cells.

TECHNICAL FIELD

The present invention relates to a cell construct for celltransplantation and a cell aggregate for cell transplantation.Specifically, the present invention relates to a cell construct for celltransplantation capable of preventing the necrosis of transplanted cellsafter transplantation and forming blood vessels at the transplantationsite, and a cell aggregate for cell transplantation capable of formingblood vessels at its transplantation site.

BACKGROUND ART

The practical utilization of regenerative medicine, which helpsregenerate living tissues/organs that have fallen into functionaldisorder or functional incompetence, is currently proceeding. Theregenerative medicine is novel medical technology of re-creating thesame or similar forms or functions as in original tissues using 3factors, i.e., cells, scaffolds, and growth factors, for living tissuesthat no longer recover by only natural healing ability intrinsicallypossessed by organisms. In recent years, treatments using cells havebeen being gradually realized. Examples thereof include culturedepidermis using autologous cells, cartilage treatment using autologouscartilage cells, bone regeneration treatment using mesenchymal stemcells, cardiac muscle cell sheet treatment using myoblasts, cornealregeneration treatment using corneal epithelial sheets, and nerveregeneration treatment. These novel treatments, unlike conventionalalternative medicine based on artificial materials (bone prostheticmaterials or hyaluronic acid injection), help repair or regeneration ofliving tissues and therefore produce high therapeutic effects. In fact,some products such as cultured epidermis or cultured cartilage usingautologous cells have been launched.

In this context, for example, the regeneration of cardiac muscle usingcell sheets is considered to require a multilayer construct of cellsheets for regenerating thick tissues. Okano et al. have recentlydeveloped cell sheets using a temperature-responsive culture dish. Thecell sheets do not require treatment with an enzyme such as trypsin andthus retain cell-to-cell binding and adhesion proteins (Non PatentDocuments 1 to 6). Such a cell sheet production technique is expected tobe useful in the regeneration of cardiac muscle tissues (Non PatentDocument 7). Okano et al. have also thought that a thickness of 200 μmor larger is impossible to achieve, and are developing cell sheets alsocontaining vascular endothelial cells introduced therein in order toform vascular network in the cell sheets (Non Patent Document 8).

Also for bone regeneration, bone regeneration sheets comprising culturedcells added to matrices have been developed.

A bone regeneration sheet prepared by layering a cultured cell sheetcomprising mesenchymal stem cells cultured into a sheet-like shape and abiodegradable sheet comprising biodegradable substances formed into asheet-like shape (Patent Document 1) has been proposed. Moreover, thereis a sheet for induction of mesenchymal tissue regeneration in whichmesenchymal tissue precursor cells differentiated from mesenchymal cellsand extracellular matrices are attached onto a porous sheet (PatentDocument 2). Then, Patent Document 3 has reported that a sheet of 200 μmor larger in thickness can be formed by the development/optimization ofa culture approach, and has also disclosed that the formation ofapproximately 210 μm cortical bone tissue layer was confirmed.

Furthermore, gel-embedding culture using collagen has been devised asone means of solving insufficient penetration of nutrients by onlydiffusion into a three-dimensional construct composed of cells (NonPatent Document 9). Moreover, Patent Document 4 states thatthree-dimensional culture is achieved by linking cells using inorganicceramic beads.

PRIOR ART DOCUMENTS

-   [Patent Document 1] JP Patent Publication (Kokai) No. 2003-275294A    (2003)-   [Patent Document 2] JP Patent Publication (Kokai) No. 2006-116212A    (2006)-   [Patent Document 3] JP Patent Publication (Kokai) No. 2009-240766A    (2009)-   [Patent Document 4] JP Patent Publication (Kokai) No. 2004-267562A    (2004)-   [Non Patent Document 1] Shimizu, T. et al., Circ. Res. 90, e40-48    (2002)-   [Non Patent Document 2] Kushida, A. et al., J. Biomed. Mater. Res.    51, 216-223 (2000)-   [Non Patent Document 3] Kushida, A. et al., J. Biomed. Mater. Res.    45, 355-362 (1999)-   [Non Patent Document 4] Shimizu, T., Yamato, M., Kikuchi, A. &    Okano, T., Tissue Eng. 7, 141-151 (2001)-   [Non Patent Document 5] Shimizu, T et al., J. Biomed. Mater. Res.    60, 110-117 (2002)-   [Non Patent Document 6] Harimoto, M. et al., J. Biomed. Mater. Res.    62, 464-470 (2002)-   [Non Patent Document 7] Shimizu, T., Yamato, M., Kikuchi, A. &    Okano, T., Biomaterials 24, 2309-2316(2003)-   [Non Patent Document 8] Inflammation and Regeneration vol. 25 No. 3    2005, p. 158-159. The 26th annual meeting of the Japanese Society of    Inflammation and Regeneration—Pursuing fusion between inflammation    research and regenerative medicine—Mitsuo Okano-   [Non Patent Document 9] Sustained growth and three-dimensional    organization of primary mammary tumor epithelial cells embedded in    collagen gel. J Yang, J Richards, P Bowman, R Guzman, J Enami, K    McCormick, S Hamamoto, D Pitelka, and S Nandi. PNAS Jul. 1, 1979    vol. 76 no. 7 3401-3405

SUMMARY OF INVENTION Object to be Solved by the Invention

Current techniques relating to regenerative medicine cannot providetissues having a sufficient thickness, because cells to be transplantedare mainly transplanted in a thin sheet form or transplanted in thestate of a suspension. Living tissues are originally thick and enablemuscle force to allow the heart to beat or permit smooth movement atarticular cartilage because of being thick. For general tissueregeneration using cells, the inability to provide thick tissues isconsidered as a major problem.

Since previous cell sheets cannot form vascular network, sufficientlythick tissues have been difficult to regenerate (Non Patent Documents 5and 7). This is because nutrition supply to cells in the central portionis lost in a cell sheet allowed to be thick, whereby the cells arekilled. Alternatively, cell sheets also containing vascular endothelialcells introduced therein (Non Patent Document 8) have been developed.However, this cannot serve as a realistic solution due to many problems:in addition to the cells of interest, another cell source, i.e.,vascular endothelial cells, must be prepared; it is difficult touniformly induce blood vessels in the cell sheet; and even if thedelivery pathway of nutrients can be provided by this means, theprepared nutrition delivery pathway must be precisely connected to anexternal nutrition delivery pathway in this approach.

In addition, the inventions described in Patent Documents 1 and 2 aboveare methods involving placing a cultured osteoblast-attached sheet intothe body and forming cortical bone from the osteoblast throughmembranous ossification in vivo. However, osteoblast-like cells cannotbe cultured in a layered state, and due to this problem, sheets havingan osteoblast layer have failed to provide regeneration sheets in whichthe thickness of a cell layer exceeds 100 μm.

As described above, it was a difficult challenge in the past to providecells as a thick composition for many tissue repairs. The leading causethereof is the insufficient penetration of nutrients by only diffusioninto a three-dimensional construct composed of cells. Gel-embeddingculture using collagen has been devised as one means of solving this(Non Patent Document 9). However, cells embedded in a gel cannot solvethis problem at its source, because the cells are moved from the centralportion of the gel toward the outer region and thus, are not uniformlypresent in the gel to reduce the cell density of the central portion.Moreover, the three-dimensional cell construct prepared by gel embeddingcannot be bound/fused to another three-dimensional construct and thus,cannot form a three-dimensional construct above the size prepared at thetime of cell inoculation. Thus, the means of preparing small gels andthen fusing the gels to each other to prepare a construct in which cellsare uniformly distributed cannot be adopted.

Moreover, as described above, Patent Document 4 states thatthree-dimensional culture is achieved by linking cells using inorganicceramic beads. However, inorganic ceramics are inferior in waterretention, solution exchange, diffusion of nutrition, and buffercapacity and cannot actually provide a thick cell composition. In fact,in Examples of Patent Document 4, cells were bonded to 150 to 460 μmparticles, over which a thick PLLA nonwoven fabric (1 cm) was layered tomerely increase an apparent thickness. The actual cell-containing layerwas merely a layer of tens of μm at the thickest on the surface of theinorganic ceramic beads. Even if the 1 cm PLLA nonwoven fabric having nocell is regarded as a construct, it is merely a construct havingsignificantly nonuniform cell distribution. Thus, only thethree-dimensional cell construct having nonuniform cell distribution inthe construct or the construct having a substantially thin cell layerhas been provided so far.

As described above, the conventional techniques have failed to providebiological materials that sufficiently meet requirements for asufficient thickness suitable for cell transplantation, prevention ofthe necrosis of transplanted cells, and blood vessel formation.Biological materials for cell transplantation that satisfy theserequirements have been demanded.

Thus, an object of the present invention is to provide a cell constructfor cell transplantation capable of having a thickness suitable for celltransplantation, preventing the necrosis of transplanted cells, andforming blood vessels in the transplantation site after transplantation.

Means for Solving the Object

As a result of conducting diligent studies to attain the object, thepresent inventors have completed the present invention by finding thatthe object can be attained by using a construct in which polymer blockshaving biocompatibility (blocks containing a polymer material havingbiocompatibility) and cells are arranged in a particular pattern as acell construct for cell transplantation intended for use in celltransplantation.

The cell construct for cell transplantation according to the presentinvention is characterized in that it comprises polymer blocks havingbiocompatibility and cells of at least one type, wherein the pluralpolymer blocks are arranged in spaces between the plural cells.

In the present invention, the polymer blocks each preferably have a sizefrom 1 μm to 700 μm, and more preferably from 10 μm to 300 μm. In thecell construct for cell transplantation according to the presentinvention, the thickness or diameter thereof is preferably from 400 μmto 3 cm, and more preferably from 720 μm to 1 cm. The ratio between thepolymer blocks and the cells is preferably from 0.0000001 μg to 1 μg ofthe polymer blocks per cell. Preferably, the cell construct for celltransplantation is produced by incubating a mixture of the polymerblocks having biocompatibility and a culture solution comprising thecells.

Preferably, the polymer having biocompatibility is a biodegradablematerial. Examples of the polymer having biocompatibility includepolypeptide, polylactic acid, polyglycolic acid, PLGA, hyaluronic acid,glycosaminoglycan, proteoglycan, chondroitin, cellulose, agarose,carboxymethylcellulose, chitin, or chitosan. Preferred examples includegelatin, collagen, elastin, fibronectin, ProNectin, laminin, tenascin,fibrin, fibroin, entactin, thrombospondin, or RetroNectin.

Preferably, the polymer having biocompatibility is cross-linked. Morepreferably, the cross-linking is performed with an aldehyde, acondensing agent, or an enzyme.

Preferably, the polymer having biocompatibility is a recombinantpeptide. Preferably, the polymer having biocompatibility has two or morecell adhesion signals in a molecule. Preferably, the recombinant peptideis represented by the formula:

A-[(Gly-X-Y)_(n)]_(m)-B

wherein A represents any amino acid or amino acid sequence; B representsany amino acid or amino acid sequence; each X of total n independentlyrepresents any amino acid; each Y of total n independently representsany amino acid; n represents an integer of 3 to 100; m represents aninteger of 2 to 10; and each Gly-X-Y of total n may be the same as ordifferent from each other.More preferably, the recombinant peptide is represented by the formula:

Gly-Ala-Pro-[(Gly-X-Y)₆₃]₃-Gly

wherein each X of total 63 independently represents any amino acid; eachY of total 63 independently represents any amino acid; and each Gly-X-Yof total 63 may be the same as or different from each other.Preferably, the recombinant peptide has (1) the amino acid sequencerepresented by SEQ ID NO: 1, or (2) an amino acid sequence having 80% orhigher homology to the amino acid sequence represented by SEQ ID NO: 1and having biocompatibility. Preferably, the cell construct for celltransplantation according to the present invention further comprises anangiogenesis factor.

Preferably, the cells in the present invention are cells selected fromthe group consisting of pluripotent cells, somatic stem cells, precursorcells, and mature cells. A cell construct for cell transplantationcomprising non-vascular cells can be preferably used as the cellconstruct for cell transplantation according to the present invention.The cell construct for cell transplantation wherein the cells are onlynon-vascular cells, can be also preferably used. Preferably, the cellsare of two or more types comprising both non-vascular cells and vascularcells. In this case, the cell construct for cell transplantationpreferably has a region wherein the area of the vascular cells in thecentral portion of the cell construct is larger than the area of thevascular cells in the peripheral portion. Further preferably, the cellconstruct for cell transplantation has a region wherein the ratio of thevascular cells in the central portion is 60% to 100% to the whole areasof the vascular cells. Preferably, the cell construct for celltransplantation has a region wherein the density of the vascular cellsin the central portion is 1.0×10⁻⁴ cells/μm³ or more. The cell constructfor cell transplantation according to the present invention may includea cell construct for cell transplantation in which blood vessels havebeen formed by using the cell construct for cell transplantationaccording to the present invention wherein the cells are of two or moretypes comprising both non-vascular cells and vascular cells.

The cell aggregate for cell transplantation according to the presentinvention is characterized in that it comprises non-vascular cells andvascular cells, wherein the cell aggregate for cell transplantationsatisfies at least one of the requirements:

(1) the cell aggregate has a region wherein the area of the vascularcells in the central portion of the cell aggregate is larger than thearea of the vascular cells in the peripheral portion, and(2) the cell aggregate has a region wherein the density of the vascularcells in the central portion is 1.0×10⁻⁴ cells/μm³ or more.

Preferably, the cell aggregate for cell transplantation according to thepresent invention satisfies both of the requirements (1) and (2).Preferably, the cell aggregate for cell transplantation has a regionwherein the ratio of the vascular cells in the central portion is 60% to100% to the whole area of the vascular cells.

The present invention further provides a method for transplanting cells,which comprises transplanting the cell construct for celltransplantation of the present invention.

The present invention further provides a method for transplanting cells,which comprises transplanting the cell aggregate for celltransplantation of claim 17 to a subject.

Effect of the Invention

The cell construct for cell transplantation of the present invention canhave a thickness suitable for cell transplantation. In addition, polymerblocks having biocompatibility (blocks containing a polymer materialhaving biocompatibility) and cells are three-dimensionally arranged in amosaic pattern, whereby a three-dimensional cell construct in which thecells are uniformly present can be formed to enable nutrition deliveryinto the three-dimensional cell construct from outside. As a result,when cell transplantation is performed using the cell construct for celltransplantation of the present invention, transplantation with thenecrosis of the transplanted cells prevented can be achieved.Furthermore, even in the case where vascular cells are not used as acell species used, the cell construct is capable of forming bloodvessels at the transplantation site after transplantation. Moreover, thecell aggregate for cell transplantation of the present invention iscapable of forming blood vessels at its transplantation site aftertransplantation.

BRIEF DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 shows a stereoscopic microscope photograph of Day 7 (chondrogenicdifferentiation medium) of a mosaic cell mass prepared using recombinantpeptide micro-blocks.

FIG. 2 shows a stereoscopic microscope photograph of Day 7 (chondrogenicdifferentiation medium) of a mosaic cell mass prepared using naturalgelatin micro-blocks.

FIG. 3 shows a photograph of a slice (HE-stained, magnification: ×5) ofthe mosaic cell mass containing the recombinant peptide micro-blocks.

FIG. 4 shows a photograph of a slice (HE-stained, magnification: ×10) ofthe mosaic cell mass containing the recombinant peptide micro-blocks.

FIG. 5 shows a photograph of a slice (HE-stained, magnification: ×40) ofthe mosaic cell mass containing the recombinant peptide micro-blocks.

FIG. 6 shows the fusion of the mosaic cell masses.

FIG. 7 shows a photograph of a HE-stained slice (magnification: ×5) fromthe fusion of the mosaic cell masses (fusion of three mosaic cellmasses).

FIG. 8 shows a photograph of a HE-stained slice (magnification: ×10)from the fusion of the mosaic cell masses (fusion of three mosaic cellmasses).

FIG. 9 shows a photograph of a HE-stained slice (magnification: ×20)from the fusion of the mosaic cell masses (fusion of three mosaic cellmasses).

FIG. 10 shows a photograph of a HE-stained slice (magnification: ×5)from the fusion of the mosaic cell masses (fusion of three mosaic cellmasses).

FIG. 11 shows a photograph of a HE-stained slice (magnification: ×10)from the fusion of the mosaic cell masses (fusion of three mosaic cellmasses).

FIG. 12 shows a stereoscopic microscope photograph (time-dependentchange) of a mosaic cell mass with an increased volume.

FIG. 13 shows time-dependent change in diameter from the stereoscopicmicroscope photograph of the mosaic cell mass with an increased volume.

FIG. 14 shows time-dependent change in area from the stereoscopicmicroscope photograph of the mosaic cell mass with an increased volume.

FIG. 15 shows time-dependent change in volume (4/3πr³) determined bycalculation from the stereoscopic microscope photograph of the mosaiccell mass with an increased volume.

FIG. 16 shows a slice (Day 7 (under the growth medium), magnification:×5) of a mosaic cell mass containing the recombinant peptidemicro-blocks.

FIG. 17 shows a slice (Day 7 (under the growth medium), magnification:×10) of a mosaic cell mass containing the recombinant peptidemicro-blocks.

FIG. 18 shows a photograph (magnification: ×5) of a HE slice of Day 21with an increased volume (the recombinant peptide blocks were addedunder the growth medium).

FIG. 19 shows a photograph (magnification: ×40) of a HE slice of Day 21with an increased volume (the recombinant peptide blocks were addedunder the growth medium).

FIG. 20 shows a photograph (magnification: ×5 and ×20) of a HE slice ofDay 21 with an increased volume (the recombinant peptide blocks wereadded under the chondrogenic differentiation medium).

FIG. 21 shows spectral data of GAG.

FIG. 22 shows time-dependent change in the amount of GAG produced in themosaic cell mass.

FIG. 23 shows the amount of ATP produced/retained by the cells in themosaic cell mass (Day 7).

FIG. 24 shows a stereoscopic microscope photograph of Day 2 (growthmedium) of a mosaic cell mass prepared using PLGA micro-blocks.

FIG. 25 shows the manner in which a mosaic cell mass consisting ofcardiac muscle cells and the recombinant peptide micro-blocks beats insynchronization as a whole.

FIG. 26 shows microscope photographs and fluorescence microscopephotographs of mosaic cell masses consisting of GFP-expressing HUVEC andthe recombinant peptide micro-blocks (a mosaic cell mass of 50000cells+0.03 mg of the micro-blocks and a mosaic cell mass of 300000cells+0.2 mg of the micro-blocks).

FIG. 27 shows a stereoscopic microscope photograph of a fused form oflarger mosaic cell masses.

FIG. 28 shows a photograph of a slice (HE-stained) of a mosaic cell masscontaining the recombinant peptide micro-blocks.

FIG. 29 shows a photograph of a slice (HE-stained) of a hMSC cell mass.

FIG. 30 shows a photograph of a slice (immunostained with an anti-CD29antibody and an anti-CD31 antibody) of a mosaic cell mass produced inExample 20-(1) using the recombinant peptide.

FIG. 31 shows a photograph of a slice (immunostained with an anti-CD29antibody and an anti-CD31 antibody) of a mosaic cell mass produced inExample 20-(2)A using the recombinant peptide.

FIG. 32 shows a photograph of a slice (immunostained with an anti-CD29antibody and an anti-CD31 antibody) of a mosaic cell mass produced inExample 20-(2)B using the recombinant peptide.

FIG. 33 shows a photograph of a slice (immunostained with an anti-CD29antibody and an anti-CD31 antibody) of a mosaic cell mass produced inExample 20-(3) using the recombinant peptide.

FIG. 34 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass(Example 19-(1)) containing the recombinant peptide micro-blocks.

FIG. 35 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of a hMSC cell mass(Comparative Example 1).

FIG. 36 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass(Example 20-(1)) containing the recombinant peptide micro-blocks.

FIG. 37 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass A(Example 20-(2)) containing the recombinant peptide micro-blocks.

FIG. 38 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass(Example 20-(3)) containing the recombinant peptide micro-blocks.

FIG. 39 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass A(Example 20-(2)) containing the recombinant peptide micro-blocks.

FIG. 40 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of the mosaic cell mass B(Example 20-(2)) containing the recombinant peptide micro-blocks.

FIG. 41 shows a photograph of a tissue slice (HE-stained) of atransplantation site after transplantation of a cell mass (B ofComparative Example 2).

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention will be describedin detail.

The cell construct for cell transplantation of the present inventioncomprises polymer blocks having biocompatibility and cells of at leastone type, wherein the plural polymer blocks are arranged in spacesbetween the plural cells. Examples of an aspect thereof include a cellconstruct comprising plural polymer blocks having biocompatibility andplural cells, wherein one or plural polymer blocks are arranged in eachof some or all of plural spaces formed by the plural cells.

The shape of the polymer blocks according to the present invention isnot particularly limited and is, for example, amorphous, spherical,particulate, powdery, porous, fibrous, spindle-like, flat, andsheet-like shapes, preferably amorphous, spherical, particulate,powdery, and porous shapes, more preferably an amorphous shape. The term“amorphous” represents a nonuniform surface shape, for example, matterhaving surface irregularities, such as rocks.

In the cell construct for cell transplantation of the present invention,plural polymer blocks are arranged in spaces between plural cells. Inthis context, the “spaces between the cells” do not have to be closedspaces created by the constituent cells and need only to be flanked bythe cells. It is not required that all the cells should create suchspaces therebetween. There may be a region in which the cells are incontact with each other. The distance of each space between the cellsvia the polymer block(s), i.e., the distance of the space from a certaincell to a selected cell located nearest from the certain cell, is notparticularly limited and is preferably, the size of polymer block(s).The preferable distance is also in the range of preferable sizes of thepolymer block(s).

Moreover, the polymer blocks according to the present invention areflanked by the cells in the constitution. It is not required that allthe polymer blocks should be flanked by the cells. There may be a regionin which the polymer blocks are in contact with each other. The distancebetween the polymer blocks via the cell(s), i.e., the distance from acertain polymer block to a selected polymer block located nearest fromthe certain polymer block, is not particularly limited and is preferablythe size of one cell used or a cell mass containing a cell population,for example, from 10 μm to 1000 μm, preferably from 10 μm to 100 μm,more preferably from 10 μm to 50 μm.

In the present specification, the phrase “uniformly present” is used, asdescribed in a “three-dimensional cell construct in which the cells areuniformly present”. However, this phrase does not mean completeuniformity but means that the cells are distributed in a range thatachieves the effects of the present invention, i.e., enables nutritiondelivery into the three-dimensional cell construct from outside,prevents the necrosis of transplanted cells, and allows blood vesselformation at the transplantation site after transplantation.

(1) Polymer Material Having Biocompatibility (1-1) Polymer Material

The polymer having biocompatibility used in the present invention is notparticularly limited by whether or not the polymer is degraded in vivoas long as it has affinity for organisms. It is preferred to be composedof a biodegradable material. A non-biodegradable material isspecifically at least one material selected from the group consisting ofPTFE, polyurethane, polypropylene, polyester, vinyl chloride,polycarbonate, acryl, stainless, titanium, silicone, and MPC(2-methacryloyloxyethyl phosphorylcholine). A biodegradable material isspecifically at least one material selected from the group consisting ofpolypeptide, polylactic acid, polyglycolic acid, PLGA(poly(lactic-co-glycolic acid)), hyaluronic acid, glycosaminoglycan,proteoglycan, chondroitin, cellulose, agarose, carboxymethylcellulose,chitin, and chitosan. Among them, polypeptide is particularlypreferable. In this context, these polymer materials may be given acontrivance to enhance cell adhesiveness. Methods such as [1] “coatingof matrix surface with a cell-adhesive substrate (fibronectin,vitronectin, and laminin) or a cell adhesion sequence (RGD sequence, LDVsequence, REDV (SEQ ID NO: 2) sequence, YIGSR (SEQ ID NO: 3) sequence,PDSGR (SEQ ID NO: 4) sequence, RYVVLPR (SEQ ID NO: 5) sequence, LGTIPG(SEQ ID NO: 6) sequence, RNIAEIIKDI (SEQ ID NO: 7) sequence, IKVAV (SEQID NO: 8) sequence, LRE sequence, DGEA (SEQ ID NO: 9) sequence, and HAVsequence, indicated by single letter codes for amino acids) peptide”,[2] “amination or cationization of matrix surface”, and [3] “plasmatreatment or corona discharge-based hydrophilic treatment of matrixsurface” may be used as specific methods.

The type of the polypeptide is not particularly limited as long as ithas biocompatibility. The polypeptide is preferably, for example,gelatin, collagen, elastin, fibronectin, ProNectin, laminin, tenascin,fibrin, fibroin, entactin, thrombospondin, or RetroNectin, mostpreferably gelatin, collagen, or atelocollagen. Natural gelatin or arecombinant peptide is preferable as gelatin for use in the presentinvention. A recombinant peptide is more preferable. In this context,the natural gelatin means gelatin formed from naturally derivedcollagen. The recombinant peptide will be described later in the presentspecification.

The hydrophilicity value “1/IOB” value of the polymer havingbiocompatibility used in the present invention is preferably 0 to 1.0,more preferably 0 to 0.6, further preferably 0 to 0.4. IOB is an indexfor hydrophilicity and hydrophobicity based on the organic conceptiondiagram representing the polarity/non-polarity of organic compoundsproposed by Atsushi Fujita. The details thereof are described in, forexample, “Pharmaceutical Bulletin”, vol. 2, 2, pp. 163-173 (1954),“Journal of Japanese Chemistry” vol. 11, 10, pp. 719-725 (1957), and“Fragrance Journal”, vol. 50, pp. 79-82 (1981). In short, this processinvolves assuming that methane (CH4) is the source of all organiccompounds and all of the other compounds are methane derivatives,selecting a certain numerical value for each of the number of carbonatoms, substituents, modified moieties, rings, and the like thereof,adding the scores to determine an organic value (OV) and an inorganicvalue (IV), and plotting this value on a diagram with the organic valueon the X axis and the inorganic value on the Y axis. IOB on the organicconception diagram refers to the ratio of the inorganic value (IV) tothe organic value (OV), i.e., “inorganic value (IV)/organic value (OV)”,on the organic conception diagram. For the details of the organicconception diagram, see “Shinban Yuuki Gainenzu—Kiso to Ouyou—(NewEdition, The Organic Conceptual Diagram, its Fundamentals andApplications in English)”, (Yoshio Koda et al., Sankyo Publishing Co.,Ltd., 2008)”. In the present specification, hydrophilicity andhydrophobicity are indicated by “1/IOB” values, reciprocals of JOB. Thisnotation represents that the smaller the “1/IOB” value becomes (the morethe “1/IOB” value approaches 0), the more hydrophilic it is.

The “1/IOB” value of the polymer used in the present invention is set towithin the range described above, whereby hydrophilicity is enhanced andwater absorbability is enhanced. The resulting polymer is presumed toeffectively act on retention of nutrients and, as a result, contributeto cell stabilization and viability in the three-dimensional cellconstruct (mosaic cell mass) of the present invention.

In the case where the polymer having biocompatibility used in thepresent invention is polypeptide, its index for hydrophilicity andhydrophobicity indicated by Grand average of hydropathicity (GRAVY)values is preferably from −9.0 to 0.3, more preferably from −7.0 to 0.0.The Grand average of hydropathicity (GRAVY) value can be obtained by themethods of “Gasteiger E., Hoogland C., Gattiker A., Duvaud S., WilkinsM. R., Appel R. D., Bairoch A.; Protein Identification and AnalysisTools on the ExPASy Server; (In) John M. Walker (ed): The ProteomicsProtocols Handbook, Humana Press (2005). pp. 571-607” and “Gasteiger E.,Gattiker A., Hoogland C., Ivanyi I., Appel R. D., Bairoch A.; ExPASy:the proteomics server for in-depth protein knowledge and analysis.;Nucleic Acids Res. 31: 3784-3788 (2003)”.

The GRAVY value of the polymer used in the present invention is set towithin the range described above, whereby hydrophilicity is enhanced andwater absorbability is enhanced. The resulting polymer is presumed toeffectively act on retention of nutrients and, as a result, contributeto cell stabilization and viability in the three-dimensional cellconstruct (mosaic cell mass; cell mass exhibiting a mosaic pattern) ofthe present invention.

(1-2) Cross-Linking

The polymer material having biocompatibility used in the presentinvention may be cross-linked or may not be cross-linked. Thosecross-linked are preferable. A method known in the art, such as thermalcross-linking, chemical cross-linking, cross-linking using an aldehyde(e.g., formaldehyde and glutaraldehyde), cross-linking using acondensing agent (carbodiimide, cyanamide, etc.), enzymaticcross-linking, photocrosslinking, UV cross-linking, hydrophobicinteraction, hydrogen bond, or ionic interaction can be used as across-linking method. A cross-linking method using glutaraldehyde or athermal cross-linking method is preferable.

Examples of the photocrosslinking include those based on lightirradiation of a polymer containing a photoreactive group introducedtherein, or light irradiation in the presence of a photosensitizer.Examples of the photoreactive group include a cinnamyl group, a coumaringroup, a dithiocarbamyl group, a xanthene dye, and camphorquinone.

In the case of performing cross-linking using an enzyme, the enzyme isnot particularly limited as long as it has the effect of cross-linkingbetween polymer materials. The cross-linking can be performed usingpreferably transglutaminase and laccase, most preferablytransglutaminase. Specific examples of proteins that may be subjected toenzymatic cross-linking with transglutaminase are not particularlylimited as long as they are proteins having a lysine residue and aglutamine residue. The transglutaminase may be derived from a mammal ormay be derived from a microbe. Specific examples thereof include ACTIVAseries manufactured by Ajinomoto Co., Inc., mammal-derivedtransglutaminase sold as reagents, for example, guinea pig liver-derivedtransglutaminase, goat-derived transglutaminase, and rabbit-derivedtransglutaminase manufactured by Oriental Yeast Co., ltd., Upstate USAInc., or Biodesign International, and human-derived blood coagulationfactor (Factor XIIIa, Haematologic Technologies, Inc.).

The cross-linking of the polymer material involves two steps: the stepof mixing a polymer material solution with a cross-linking agent and thestep of reacting the resulting solution.

In the present invention, the mixing temperature for the treatment ofpolymer materials with a cross-linking agent is not particularly limitedas long as the solution can be mixed. The temperature is preferably 0°C. to 100° C., more preferably 0° C. to 40° C., further preferably 0° C.to 30° C., further preferably 3° C. to 25° C., further preferably 3° C.to 15° C., further preferably 3° C. to 10° C., particularly preferably3° C. to 7° C.

The temperature can be raised for the step of reacting the polymermaterials with the cross-linking agent. The reaction temperature is notparticularly limited as long as the cross-linking proceeds. Inconsideration of the denaturation or degradation of the polymermaterials, the temperature is substantially −100° C. to 200° C., morepreferably 0° C. to 60° C., more preferably 0° C. to 40° C., furtherpreferably 3° C. to 25° C., further preferably 3° C. to 15° C., furtherpreferably 3° C. to 10° C., particularly preferably 3° C. to 7° C.

Even if the cross-linking agent is not used, the cross-linking of thepolymer material can also be performed. Specific examples of thecross-linking method include, but not particularly limited to, a thermalcross-linking method.

The reaction temperature for the cross-linking method without using thecross-linking agent is not particularly limited as long as thecross-linking can be performed. The temperature is preferably −100° C.to 500° C., more preferably 0° C. to 300° C., further preferably 50° C.to 300° C., further preferably 100° C. to 250° C., further preferably120° C. to 200° C.

(1-3) Recombinant Peptide

The recombinant peptide according to the present invention means apolypeptide or a protein-like substance that is prepared by a generecombination technique and has an amino acid sequence similar togelatin. For the recombinant peptide that can be used in the presentinvention, it is preferred to have repeats of the sequence representedby Gly-X-Y (X and Y each independently represent any amino acid)characteristic of collagen (a plurality of Gly-X-Y sequences may be thesame as or different from each other). Preferably, two or more sequencesof cell adhesion signals are contained in a molecule. A recombinantpeptide having an amino acid sequence derived from a partial amino acidsequence of collagen can be used as the recombinant peptide used in thepresent invention. For example, those described in EP1014176, U.S. Pat.No. 6,992,172, WO2004/85473, and WO2008/103041 can be used, though therecombinant peptide is not limited to them. A preferable recombinantpeptide used in the present invention is a recombinant peptide havingthe following aspect:

The recombinant peptide used in the present invention is excellent inbiocompatibility based on the original performance of natural gelatin,is free from concerns about BSE or the like because of being notnaturally derived, and is also excellent in non-infectious properties.Moreover, since the recombinant peptide used in the present invention ishomogeneous compared with natural one and its sequence is determined, itcan be designed precisely with a little variation in strength ordegradability depending on cross-linking or the like described later.

The molecular weight of the recombinant peptide is preferably from 2 KDato 100 KDa, more preferably from 2.5 KDa to 95 KDa, further preferablyfrom 5 KDa to 90 KDa, most preferably from 10 KDa to 90 KDa.

The recombinant peptide has repeats of the sequence represented byGly-X-Y characteristic of collagen. In this context, a plurality ofGly-X-Y sequences may be the same as or different from each other. InGly-X-Y, Gly represents glycine, and X and Y each represent any aminoacid (preferably, any amino acid other than glycine). The GXY sequencecharacteristic of collagen is a very specific partial structure in theamino acid composition and sequence of gelatin/collagen, compared withother proteins. In this moiety, glycine accounts for approximately ⅓ ofthe whole and appears at a rate of one out of three amino acids in theamino acid sequence. Glycine is the simplest amino acid. Its position inthe molecular chain is less restricted, and glycine makes a significantcontribution to the regeneration of the helix structure duringgelatinization. It is preferred that imino acids (proline or oxyproline)should be included in large amounts in the amino acids represented by Xand Y and account for 10% to 45% of all the amino acids. It is preferredthat preferably 80% or more, more preferably 95% or more, mostpreferably 99% or more of the amino acids in the sequence should formthe GXY repeat structures.

In general gelatin, of polar amino acids, those having an electriccharge and those uncharged are present at a 1:1 ratio. In this context,the polar amino acids specifically refer to cysteine, aspartic acid,glutamic acid, histidine, lysine, asparagine, glutamine, serine,threonine, tyrosine, and arginine. Of them, polar uncharged amino acidsrefer to cysteine, asparagine, glutamine, serine, threonine, andtyrosine. The ratio of the polar amino acids is 10 to 40%, preferably 20to 30%, to all amino acids constituting the recombinant peptide used inthe present invention. In addition, it is preferred that the ratio ofuncharged amino acids to the polar amino acids should be from 5% to lessthan 20%, preferably less than 10%. It is further preferred that ofserine, threonine, asparagine, tyrosine and cysteine, any one aminoacid, preferably two or more amino acids, should not be contained in thesequence.

In general, minimal ammo acid sequences that function as cell adhesionsignals in polypeptides are known (e.g., “Medicina Philosophica”, Vol.9, No. 7 (1990), p. 527, Nagai Shoten Co., Ltd.). It is preferred thatthe recombinant peptide used in the present invention should have two ormore of these cell adhesion signals in a molecule. Specific sequencesare preferably RGD sequences, LDV sequences, REDV (SEQ ID NO: 2)sequences, YIGSR (SEQ ID NO: 3) sequences, PDSGR (SEQ ID NO: 4)sequences, RYVVLPR (SEQ ID NO: 5) sequences, LGTIPG (SEQ ID NO: 6)sequences, RNIAEIIKDI (SEQ ID NO: 7) sequences, IKVAV (SEQ ID NO: 8)sequences, LRE sequences, DGEA (SEQ ID NO: 9) sequences, and HAVsequences, more preferably RGD sequences, YIGSR (SEQ ID NO: 3)sequences, PDSGR (SEQ ID NO: 4) sequences, LGTIPG (SEQ ID NO: 6)sequences, IKVAV (SEQ ID NO: 8) sequences, and HAV sequences,particularly preferably RGD sequences, indicated by single letter codesfor amino acids, in terms of many types of adhesive cells. Of the RGDsequences, an ERGD (SEQ ID NO: 10) sequence is preferable. The amount ofsubstrates produced by the cells can be improved by using therecombinant peptide having cell adhesion signals. In the case of, forexample, chondrogenic differentiation using mesenchymal stem cells asthe cells, the production of glycosaminoglycan (GAG) can be improved.

For the arrangement of the RGD sequences in the recombinant peptide usedin the present invention, it is preferred that the number of amino acidsbetween the RGD sequences should be between 0 and 100, preferablybetween 25 and 60, and should not be uniformly determined.

From the viewpoint of cell adhesion/growth, the content of this minimalamino acid sequence is preferably 3 to 50 sequences, more preferably 4to 30 sequences, particularly preferably 5 to 20 sequences, mostpreferably 12 sequences, per protein molecule.

In the recombinant peptide used in the present invention, the ratio ofthe RGD motifs to the total number of the amino acids is preferably atleast 0.4%. In the case where the recombinant peptide contains 350 ormore amino acids, it is preferred that each stretch of 350 amino acidsshould contain at least one RGD motif. The ratio of the RGD motifs tothe total number of the amino acids is more preferably at least 0.6%,further preferably at least 0.8%, further preferably at least 1.0%,further preferably at least 1.2%, most preferably at least 1.5%. Thenumber of the RGD motifs within the recombinant peptide is preferably atleast 4, more preferably 6, further preferably 8, further preferablyfrom 12 to 16, per 250 amino acids. The ratio of the RGD motifs of 0.4%corresponds to at least one RGD sequence per 250 ammo acids. Since thenumber of the RGD motifs is an integer, gelatin consisting of 251 aminoacids must contain at least two RGD sequences in order to satisfy thefeature of 0.4%. Preferably, the recombinant peptide of the presentinvention contains at least two RGD sequences per 250 amino acids, morepreferably at least three RGD sequences per 250 amino acids, furtherpreferably at least four RGD sequences per 250 amino acids. In a furtheraspect, the recombinant peptide of the present invention comprises atleast 4 RGD motifs, preferably 6, more preferably 8, further preferably12 to 16 RGD motifs.

Moreover, the recombinant peptide may be partially hydrolyzed.

It is preferred that the recombinant peptide used in the presentinvention should have repeat structures represented by A[(Gly-X-Y)n]mB.m is preferably 2 to 10, more preferably 3 to 5. n is preferably 3 to100, more preferably 15 to 70, most preferably 50 to 65.

It is preferred that a plurality of naturally occurring collagensequence units should be bonded to form repeat units. In this context,the naturally occurring collagen may be any naturally occurring collagenand is preferably type-I, type-II, type-III, type-IV, and type-Vcollagens, more preferably type-I, type-II, and type-III collagens. Inanother embodiment, the origin of the collagen is preferably a human,cattle, a pig, a mouse, or a rat, more preferably a human.

The isoelectric point of the recombinant peptide used in the presentinvention is preferably 5 to 10, more preferably 6 to 10, furtherpreferably 7 to 9.5.

Preferably, the recombinant peptide is not deaminated.

Preferably, the recombinant peptide does not have telopeptide.

Preferably, the recombinant peptide is a material for substantially purecollagen prepared from a nucleic acid encoding natural collagen.

The recombinant peptide used in the present invention is particularlypreferably a recombinant peptide having;

(1) the amino acid sequence represented by SEQ ID NO: 1; or(2) an amino acid sequence having 80% or higher (more preferably 90% orhigher, most preferably 95% or higher) homology to the amino acidsequence represented by SEQ ID NO: 1 and having biocompatibility.

The recombinant peptide used in the present invention can be produced bya gene recombination technique known by those skilled in the art and canbe produced according to a method described in, for example,EP1014176A2, U.S. Pat. No. 6,992,172, WO2004-85473, or WO2008/103041.Specifically, a gene encoding the amino acid sequence of thepredetermined recombinant peptide is obtained, and this is incorporatedin an expression vector to prepare a recombinant expression vector,which is then introduced in appropriate hosts to prepare transformants.The obtained transformants are cultured in an appropriate medium,whereby the recombinant peptide is produced. Thus, the producedrecombinant peptide can be collected from the cultures to prepare therecombinant peptide used in the present invention.

(1-4) Polymer Blocks Having Biocompatibility

In the present invention, blocks containing the above-described polymermaterial having biocompatibility are used. A production method for thepolymer blocks is not particularly limited. For example, solid matterconsisting of the polymer can be pulverized using a pulverizer (NewPower Mill, etc.) and then sized through a sieve to obtain a blockhaving the desired size.

The size of each polymer block is preferably from 1 μm to 700 μm, morepreferably from 10 μm to 700 μm, further preferably from 10 μm to 300μm, further preferably from 20 μm to 150 μm, particularly preferablyfrom 25 μm to 106 μm. Moreover, the polymer block may be in a longstring-like form equal to or longer than 700 μm having a thickness inthe size range described above and may be in a sheet or gel form havinga thickness in the size range described above. The cells can be moreuniformly present in the construct by adopting this preferable range.

It is also preferred that the cell construct for cell transplantation ofthe present invention should further comprise an angiogenesis factor. Inthis context, examples of the angiogenesis factor can preferably includebasic fibroblast growth factor (bFGF), vascular endothelial growthfactor (VEGF), and hepatocyte growth factor (HGF). A method forproducing the cell construct for cell transplantation comprising anangiogenesis factor is not particularly limited. For example, this cellconstruct can be produced by using polymer blocks impregnated with anangiogenesis factor.

(2) Cells

The cells used in the present invention can be used appropriately aslong as they permit cell transplantation, which is the purpose of thecell construct of the present invention. The type thereof is notparticularly limited. Moreover, the cells used may be of one type, or acombination of a plurality of types may be used. Furthermore, the cellsused are preferably animal cells, more preferably vertebrate-derivedcells, particularly preferably human-derived cells. The type of thevertebrate-derived cells (particularly, human-derived cells) may be anyof pluripotent cells, somatic stem cells, precursor cells, and maturecells. For example, ES cells, GS cells, or iPS cells can be used aspluripotent cells. For example, mesenchymal stem cells (MSCs),hematopoietic stem cells, amnion cells, cord blood cells, bonemarrow-derived cells, cardiac muscle stem cells, fat-derived stem cells,or neural stem cells can be used as somatic stem cells. For example,cells derived from the skin, dermis, epidermis, muscle, cardiac muscle,nerve, bone, cartilage, endothelium, brain, epithelium, heart, kidney,liver, pancreas, spleen, oral cavity, cornea, bone marrow, cord blood,amnion, or hair can be used as precursor cells and mature cells. Forexample, ES cells, iPS cells, MSCs, cartilage cells, osteoblasts,osteoprogenitor cells, mesenchyme cells, myoblasts, cardiac musclecells, cardiac myoblasts, nerve cells, hepatic cells, beta cells,fibroblasts, corneal endothelial cells, vascular endothelial cells,corneal epithelial cells, amnion cells, cord blood cells, bonemarrow-derived cells, or hematopoietic stem cells can be used ashuman-derived cells. Moreover, the origin of the cells may be any ofautologous cells and heterologous cells.

Examples of cells suitable for heat diseases such as severe heartfailure and severe myocardial infarction can preferably includeautologously or heterologously extracted cardiac muscle cells, smoothmuscle cells, fibroblasts, skeletal muscle-derived cells (particularly,satellite cells), and bone marrow cells (particularly, bone marrow cellsdifferentiated into cardiac muscle-like cells). Furthermore, cells to betransplanted can be selected appropriately for other organs. Preferableexamples thereof can include transplantation of neural precursor cellsor cells capable of being differentiated into nerve cells into acerebral ischemia/cerebral infarction site, and transplantation ofvascular endothelial cells or cells capable of being differentiated intovascular endothelial cells into a myocardial infarction/skeletal muscleischemia site.

Further examples of the cells include cells for use in celltransplantation for diabetic organ damage. Specific examples thereofinclude cells for a cell transplantation treatment method variouslystudied on diseases such as kidney diseases, pancreas diseases,peripheral nerve diseases, eye diseases, or hematogenous disorder in theextremities. Specifically, an attempt to transplant insulin-secretingcells to the pancreas having the reduced ability to secrete insulin,transplantation of bone marrow-derived cells for hematogenous disorderin the extremities, or the like has been studied, and such cells can beused.

The cell construct for cell transplantation of the present inventioncomprising non-vascular cells can be used preferably. Moreover, the cellconstruct for cell transplantation of the present invention containingonly non-vascular cell as its constituent cells can also be usedpreferably. The cell construct for cell transplantation of the presentinvention containing only non-vascular cells as the cells is capable offorming blood vessels at its transplantation site after transplantation.Furthermore, in the case where the cell construct for celltransplantation of the present invention contains two or more types ofconstituent cells comprising both non-vascular cells and vascular cells,this cell construct is more capable of forming blood vessels and thusmore preferable than the cell construct containing only non-vascularcells as the constituent cells.

Furthermore, in the case where the cell construct for celltransplantation of the present invention contains two or more types ofconstituent cells and has a region wherein the area of the vascularcells in the central portion of the cell construct is larger than thearea of the vascular cells in the peripheral portion, this cellconstruct is much more capable of forming blood vessels and thus muchmore preferable. The phrase “has a region wherein the area of thevascular cells in the central portion of the cell construct is largerthan the area of the vascular cells in the peripheral portion”specifically refers to that, when slice samples having a thickness of 2μm are prepared, there is a sample having a region as defined above. Inthis context, the central portion of the cell construct refers to anarea corresponding to a distance up to 80% from the center in thedistance from the center to the surface of the cell construct. Theperipheral portion of the cell construct refers to an area from theposition of 80% from the center to the surface of the construct. In thiscontext, the central portion of the cell construct is defined asfollows:

With regard to any cross section that passes the center of the cellconstruct, a radius X is determined such that, when the center of acircle with the radius X is moved around the cross section along withthe external margin of the cross section, the area of a portion exceptfor the overlap between the moved circle and the cross section accountsfor 64% of the cross-sectional area of the cross section. The center ofa circle with the determined radius X is moved therearound, and aportion except for the overlap between the moved circle and the crosssection is defined as the central portion of the cell construct. At thistime, the cross section which gives largest cross-section area is mostpreferable. As to the center of the cell construct, with regard to thecross section which gives largest cross-section area, a radius Y isdetermined such that, when the center of a circle with the radius Y ismoved around the cross section along with the external margin of thecross section, the area of a portion except for the overlap between themoved circle and the cross section becomes one point. The center of acircle with the determined radius Y is moved therearound, and one pointexcept for the overlap between the moved circle and the cross section isdefined as the center of the cell construct. When the area does notbecome one point, and becomes a line segment, or when there are pluralsuch line segments, the middle point of each such line segment isdefined as the center.

Specifically, the cell construct preferably has a region wherein theratio of the vascular cells in the central portion is preferably 60% to100%, more preferably 65% to 100%, further preferably 80% to 100%,further preferably 90% to 100%, to the whole area of the vascular cells.The phrase “has a region wherein the ratio of the vascular cells in thecentral portion is 60% to 100% to the whole area of the vascular cells”specifically refers to that, when slice samples having a thickness of 2μm are prepared, there is a sample having a region having the ratio asdefined above. Blood vessel formation can be further promoted byadopting this range.

In this context, the ratio of the vascular cells in the central portioncan be determined, for example, by: staining vascular cells to beassayed when a thin section sample is prepared; determining an averagevalue of the color density (strength) of the central portion using imageprocessing software ImageJ; calculating area×strength for the centralportion; further determining an average value of color density(strength) as a whole; calculating area×strength as a whole; anddetermining the ratio of the value of area×strength for the centralportion to the value of area×strength as a whole. In this context, astaining method known in the art can be used appropriately as a methodfor staining the vascular cells. For example, in the case of usinghECFCs as the cells, an anti-CD31 antibody can be used.

It is also preferred that the cell construct should have a region inwhich the density of the vascular cells in the central portion is1.0×10⁻⁴ cells/μm³ or more. It is more preferred that the whole centralportion of the cell construct should have the cell density describedabove. In this context, the phrase “have a region in which the densityis 1.0×10⁻⁴ cells/μm³ or more” specifically means that there is a samplehaving the region with the density as mentioned above, when sectionsamples having a thickness of 2 μm are prepared. The cell density ismore preferably 1.0×10⁻⁴ to 1.0×10⁻³ cells/μm³, further preferably1.0×10⁻⁴ to 2.0×10⁻⁴ cells/μm³, further preferably 1.1×10⁻⁴ to 1.8×10⁻⁴cells/μm³, further preferably 1.4×10⁻⁴ to 1.8×10⁻⁴ cells/μm³. Bloodvessel formation can be further promoted by adopting this range.

In this context, the density of the vascular cells in the centralportion can be determined by actually counting the number of cells in athin section sample and dividing the number of cells by volume. In thiscontext, the central portion is defined as follows: it is defined as aportion obtained by cutting out a portion corresponding to the thicknessof the thin section sample in the perpendicular direction in the centralportion described above. In order to determine the cell density, thenumber of the vascular cells in the central portion can be calculated,for example, by superimposing a thin section sample in which thevascular cells to be assayed have been stained and a thin section samplein which cell nuclei have been stained and counting the number ofoverlapping cell nuclei, and the volume can be determined by determiningthe area of the central portion using ImageJ and multiplying the area bythe thickness of the thin section sample.

In the present specification, the vascular cells mean cells related toblood vessel formation and include cells constituting blood vessels orblood, and precursor cells or somatic stem cells capable of beingdifferentiated into these cells. In this context, the vascular cells donot include pluripotent cells such as ES cells, GS cells, or iPS cells,or cells that are not spontaneously differentiated into cellsconstituting blood vessels or blood, such as mesenchymal stem cells(MSC). The vascular cells are preferably cells constituting bloodvessels. Examples of the cells constituting blood vessels amongvertebrate-derived cells (particularly, human-derived cells) canpreferably include vascular endothelial cells and vascular smooth musclecells. The vascular endothelial cells include both venous endothelialcells and arterial endothelial cells. Vascular endothelial precursorcells can be used as precursor cells for the vascular endothelial cells.Vascular endothelial cells and vascular endothelial precursor cells arepreferable. Blood cells can be used as cells constituting blood, andwhite blood cells such as lymphocytes or neutrophils, monocytes, orhematopoietic stem cells as their stem cells can be used. Moreover, inthe present specification, the non-vascular cells mean cells other thanthe vascular cells described above. For example, ES cells, iPS cells,mesenchymal stem cells (MSCs), cardiac muscle stem cells, cardiac musclecells, fibroblasts, myoblasts, cartilage cells, myoblasts, hepaticcells, or nerve cells can be used. Preferably, mesenchymal stem cells(MSCs), cartilage cells, myoblasts, cardiac muscle stem cells, cardiacmuscle cells, hepatic cells, or iPS cells can be used. Mesenchymal stemcells (MSCs), cardiac muscle stem cells, cardiac muscle cells, ormyoblasts are more preferable.

The cell construct for cell transplantation of the present inventionencompasses those in which blood vessels have been formed using the cellconstruct for cell transplantation of the present invention wherein thecells are of two or more types comprising both non-vascular cells andvascular cells. Moreover, in this context, the preferable ranges of the“cell construct for cell transplantation of the present inventionwherein the cells are of two or more types comprising both non-vascularcells and vascular cells” are as described above. Examples of a methodfor constructing blood vessels include a method involving bonding a cellsheet containing a vascular cell mixture to a gel material of which apiece for a blood vessel moiety has been hollowed out in a tunnel shape,and culturing the cell sheet while flowing a culture solution to thetunnel. Alternatively, vascular cells may be sandwiched between cellsheets to construct blood vessels.

(3) Cell Construct

In the present invention, the above-described polymer blocks havingbiocompatibility and the above-described cells are used, and the pluralpolymer blocks are three-dimensionally arranged in spaces between theplural cells in a mosaic pattern, whereby the cell construct can have athickness suitable for cell transplantation. In addition, the polymerblocks having biocompatibility and the cells are three-dimensionallyarranged in a mosaic pattern, whereby a three-dimensional cell constructin which the cells are uniformly present can be formed to enablenutrition delivery into the three-dimensional cell construct fromoutside. As a result, when cell transplantation is performed using thecell construct for cell transplantation of the present invention,transplantation with the necrosis of the transplanted cells preventedcan be achieved. In this context, the “prevention of necrosis” meansthat the degree of necrosis is low compared with the case where only thecells are transplanted without being contained in the cell construct ofthe present invention.

The thickness or diameter of the cell construct for cell transplantationof the present invention can be set to the desired thickness by a methoddescribed later in the present specification and is preferably 215 μm orlarger, more preferably 400 μm or larger, most preferably 730 μm orlarger, in terms of the lower limit. The upper limit of the thickness ordiameter is not particularly limited and is preferably 3 cm or smaller,more preferably 2 cm or smaller, further preferably 1 cm or smaller, interms of a general range in use. Moreover, the range of the thickness ordiameter of the cell construct is preferably from 400 μm to 3 cm, morepreferably from 500 μm to 2 cm, further preferably from 720 μm to 1 cm.In Examples, 720 μm or larger cell constructs (FIG. 3) were prepared andthen fused to prepare a cell construct having a thickness of 813 μm(FIG. 10). A feature of the cell construct for cell transplantation ofthe present invention is that regions consisting of the polymer blocksand regions consisting of the cells are arranged in a mosaic pattern. Inthe present specification, the “thickness or diameter of the cellconstruct” represents the following: when a certain point A in the cellconstruct is selected, the length of a line segment that is located on astraight line passing through the point A and partitions the cellconstruct to give the shortest distance between the cell construct andthe outside world is defined as a line segment A. The point A isselected such that the line segment A becomes longest in the cellconstruct. The length of this longest line segment A is defined as the“thickness or diameter of the cell construct”.

Moreover, in the case of using the cell construct of the presentinvention as a cell construct before fusion or as a cell constructbefore addition of second polymer blocks in a method (described later)for producing the cell construct for cell transplantation of the presentinvention, the range of the thickness or diameter of the cell constructis preferably from 10 μm to 1 cm, more preferably from 10 μm to 2000 μm,further preferably from 15 μm to 1500 μm, most preferably from 20 μm to1300 μm.

In the cell construct for cell transplantation of the present invention,the ratio between the cells and the polymer blocks is not particularlylimited and is preferably a ratio of the polymer blocks per cell from0.0000001 μg to 1 μg, more preferably from 0.000001 μg to 0.1 μg,further preferably from 0.00001 μg to 0.01 μg, most preferably from0.00002 μg to 0.006 μg. The cells can be more uniformly present byadopting the range described above. Moreover, the cells can exerteffects during use in the application described above by adopting therange described above as the lower limit. Components arbitrarily presentin the polymer blocks can be supplied to the cells by adopting the rangedescribed above as the upper limit. In this context, examples of thecomponents in the polymer blocks include, but not particularly limitedto, components contained in a medium described later.

(4) Method for Producing Cell Construct

The cell construct of the present invention can be produced by placingthe block(s) consisting of the polymer material having biocompatibilityand the cell(s) in an alternating manner. A production method is notparticularly limited and is preferably a method involving formingpolymer blocks and then inoculating cells thereto. Specifically, thecell construct of the present invention can be produced by incubating amixture of the polymer blocks having biocompatibility and a culturesolution containing the cells. For example, the cells and the polymerblocks having biocompatibility prepared in advance are arranged in amosaic pattern in a container or in a liquid retained in a container.Means of this arrangement is preferably use of natural aggregation, freefall, centrifugation, or stirring to promote or control the sequenceformation of the mosaic pattern consisting of the cells and thebiocompatible matrices.

The container used is preferably a container made of a low cell-adhesivematerial or a non-cell-adhesive material, more preferably a containermade of polystyrene, polypropylene, polyethylene, glass, polycarbonate,or polyethylene terephthalate. It is preferred that the container shouldhave a flat, U-shaped, or V-shaped bottom.

The mosaic-pattern cell construct obtained by the method described abovecan be produced into a cell construct having the desired size by amethod, for example,

(1) fusing separately prepared mosaic-pattern cell masses with eachother, or(2) increasing the volume thereof under a differentiation medium orgrowth medium.A method for this fusion or increase in volume is not particularlylimited.

For example, in the step of incubating a mixture of the polymer blockshaving biocompatibility and a culture solution containing the cells, themedium is replaced by a differentiation medium or growth medium, wherebythe volume of the cell construct can be increased. Preferably, in thestep of incubating a mixture of the polymer blocks havingbiocompatibility and a culture solution containing the cells, additionalpolymer blocks having biocompatibility can be added thereto to produce acell construct of the desired size in which the cells are uniformlypresent.

The method involving fusing separately prepared mosaic-pattern cellmasses with each other is specifically a method for producing the cellconstruct which comprises the step of fusing cell constructs with eachother, the cell constructs each comprising plural polymer blocks havingbiocompatibility and plural cells, wherein one or more of the polymerblocks are placed in each of some or all of spaces formed by the pluralcells.

The preferable ranges of the “polymer blocks (type, size, etc.) havingbiocompatibility”, the “cells”, the “spaces between the cells”, the“obtained cell construct (size, etc.)”, the “ratio between the cells andthe polymer blocks”, and the like according to the method for producingthe cell construct of the present invention are similar to thepreferable ranges relating to the cell construct of the presentinvention described above.

Moreover, the thickness or diameter of each cell construct before thefusion is preferably from 10 μm to 1 cm, and the thickness or diameterafter the fusion is preferably from 400 μm to 3 cm. In this context, thethickness or diameter of each cell construct before the fusion is morepreferably from 10 μm to 2000 μm, further preferably from 15 μm to 1500μm, most preferably from 20 μm to 1300 μm, and the range of thethickness or diameter after the fusion is more preferably from 500 μm to2 cm, further preferably from 720 μm to 1 cm.

The above-described method for producing the cell construct of thedesired size by adding thereto additional polymer blocks havingbiocompatibility is specifically a method for producing the cellconstruct which comprises the steps of further adding second polymerblocks to a cell construct and incubating them, the cell constructcomprising plural first polymer blocks having biocompatibility andplural cells, wherein one or more of the polymer blocks are placed ineach of some or all of plural spaces formed by the plural cells. In thiscontext, the preferable ranges of the “polymer blocks (type, size, etc.)having biocompatibility”, the “cells”, the “spaces between the cells”,the “obtained cell construct (size, etc.)”, the “ratio between the cellsand the polymer blocks”, and the like are similar to the preferableranges relating to the cell construct of the present invention describedabove.

In this context, it is preferred that the cell constructs to be fusedshould be placed at a spacing from 0 to 50 μm, more preferably from 0 to20 μm, further preferably from 0 to 5 μm. In the fusion of the cellconstructs, the cells or substrates produced by the cells are consideredto function as an adhesive by cell growth/spreading to connect the cellconstructs. The adhesion between the cell constructs can be facilitatedby adopting the range described above.

The size of each first polymer block according to the present inventionis preferably from 1 μm to 700 μm, more preferably from 10 μm to 700 μm,further preferably from 10 μm to 300 μm, further preferably from 20 μmto 150 μm, particularly preferably from 25 μm to 106 μm. Moreover, thesize of each second polymer block according to the present invention isalso preferably from 1 μm to 700 μm, more preferably from 10 μm to 700μm, further preferably from 10 μm to 300 μm, further preferably from 20μm to 150 μm, particularly preferably from 25 μm to 106 μm.

The range of the thickness or diameter of the cell construct obtained bythe method for producing the cell construct of the present invention ispreferably from 400 μm to 3 cm, more preferably from 500 μm to 2 cm,further preferably from 720 μm to 1 cm.

For further adding second polymer blocks to the cell construct andincubating them, it is preferred that the pace at which the secondpolymer blocks are added should be selected appropriately according tothe growth rate of the cells used. Specifically, if the second polymerblocks are added at a fast pace, the cells are moved toward the outerregion of the cell construct to reduce uniform cell distribution. Ifthey are added at a slow pace, sites with a high ratio of the cells areformed to reduce uniform cell distribution. Thus, the pace is selectedin consideration of the growth rate of the cells used.

When cell transplantation is performed using the cell construct for celltransplantation of the present invention containing no vascular cell,even this cell construct for cell transplantation of the presentinvention, as described above, is capable of forming blood vessels atthe transplantation site after transplantation. In the case ofcomprising both non-vascular cells and vascular cells, the cellconstruct is more capable of forming blood vessels than the cellconstruct containing only non-vascular cells as the constituent cells.

Examples of the method for producing the cell construct comprising bothnon-vascular cells and vascular cells can preferably include productionmethods (1) to (3) described below.

The production method (1) comprises the steps of forming a cellconstruct by the method described above using non-vascular cells andthen adding vascular cells and polymer blocks thereto. In this context,the “step of vascular cells and polymer blocks” encompasses both of themethod involving fusing prepared mosaic-pattern cell masses with eachother and the method involving increasing the volume thereof under adifferentiation medium or growth medium. This method enables productionof (i) a cell construct in which the non-vascular cells are present in alarger area compared with the vascular cells in the central portion ofthe cell construct while the vascular cells are present in a larger areacompared with the non-vascular cells in the peripheral portion, (ii) acell construct for cell transplantation in which the area of thenon-vascular cells in the central portion of the cell construct islarger than the area of the non-vascular cells in the peripheralportion, and (iii) a cell construct for cell transplantation in whichthe area of the vascular cells in the central portion of the cellconstruct is smaller than the area of the vascular cells in theperipheral portion.

The production method (2) comprises the steps of forming a cellconstruct by the method described above using vascular cells and thenadding non-vascular cells and polymer blocks thereto. In this context,the “step of non-vascular cells and polymer blocks” encompasses both ofthe method involving fusing prepared mosaic-pattern cell masses witheach other and the method involving increasing the volume thereof undera differentiation medium or growth medium. This method enablesproduction of (i) a cell construct in which the vascular cells arepresent in a larger area compared with the non-vascular cells in thecentral portion of the cell construct while the non-vascular cells arepresent in a larger area compared with the vascular cells in theperipheral portion, (ii) a cell construct for cell transplantation inwhich the area of the vascular cells in the central portion of the cellconstruct is larger than the area of the vascular cells in theperipheral portion, and (iii) a cell construct for cell transplantationin which the area of the non-vascular cells in the central portion ofthe cell construct is smaller than the area of the non-vascular cells inthe peripheral portion.

The production method (3) involves substantially simultaneously usingnon-vascular cells and vascular cells to form a cell construct by themethod described above. This method enables production of a cellconstruct in which neither non-vascular cells nor vascular cells arelargely maldistributed at any site of the cell construct.

From the viewpoint of forming blood vessels at a transplantation siteafter transplantation, it is preferred to be a cell construct in whichthe vascular cells are present in a larger area compared with thenon-vascular cells in the central portion of the cell construct whilethe non-vascular cells are present in a larger area compared with thevascular cells in the peripheral portion, or a cell construct for celltransplantation in which the area of the vascular cells in the centralportion is larger than the area of the vascular cells in the peripheralportion. Blood vessel formation can be further promoted by adopting suchcell construct. The cell construct in which the number of the cellspresent in the central portion is larger can further promote bloodvessel formation.

For similar reasons, the production method comprising the steps offorming a cell construct using vascular cells and then adding theretonon-vascular cells and polymer blocks is preferable. For the productionmethod, it is further preferred that the number of the vascular cellsshould be increased.

The cell construct for cell transplantation of the present invention canbe used for the purpose of cell transplantation at a diseased site in,for example, heart diseases such as severe heart failure and severemyocardial infarction, and cerebral ischemia/cerebral infarction. Thecell construct can also be used for diseases such as diabetic kidneydiseases, pancreas diseases, peripheral nerve diseases, eye diseases, orhematogenous disorder in the extremities. For example, incision,injection, or endoscopy may be used as a transplantation method. Thecell construct of the present invention may be transplanted by a lowinvasive method such as transplantation by injection, because the sizeof the construct, unlike cell transplants such as cell sheets, can bedecreased.

Moreover, the cell transplantation method of the present inventioncomprises using a cell construct for cell transplantation, which is thecell construct for cell transplantation of the present invention,comprising polymer blocks having biocompatibility and cells of at leastone type, wherein the plural polymer blocks are placed in spaces betweenthe plural cells. The preferable ranges of the cell construct for celltransplantation are as described above.

The cell aggregate for cell transplantation of the present invention isa cell aggregate for cell transplantation comprising non-vascular cellsand vascular cells, wherein the cell aggregate for cell transplantationsatisfies at least one of the requirements:

(1) the cell aggregate has a region wherein the area of the vascularcells in the central portion of the cell aggregate is larger than thearea of the vascular cells in the peripheral portion, and(2) the cell aggregate has a region in which the density of the vascularcells in the central portion is 1.0×10⁻⁴ cells/μm³ or more.

In this context, the cell aggregate for cell transplantation accordingto the present invention refers to a cell transplant comprising cells asconstituents and is not intended to exclude those containing the othercomponents. The cell aggregate for cell transplantation of the presentinvention may contain the polymer blocks used for the cell construct ofthe present invention or may not contain the polymer blocks used for thecell construct of the present invention.

Examples of the shape of the cell aggregate can preferably include, butnot particularly limited to, a sheet-like shape and a spherical mass. Itcan be exemplified specifically by a cell sheet, layered product ofplural cell sheets, a cell mass (spheroid), and fused product of pluralcell masses.

Moreover, the non-vascular cells and the vascular cells are as describedabove.

The central portion of the cell aggregate refers to an areacorresponding to a distance up to 80% from the center in the distancefrom the center to the surface of the cell aggregate. The peripheralportion of the cell aggregate refers to an area from the position of 80%from the center to the surface of the construct. In this context, thecentral portion of the cell aggregate is defined as follows:

With regard to any cross section that passes the center of the cellconstruct, a radius X is determined such that, when the center of acircle with the radius X is moved around the cross section along withthe external margin of the cross section, the area of a portion exceptfor the overlap between the moved circle and the cross section accountsfor 64% of the cross-sectional area of the cross section. The center ofa circle with the determined radius X is moved therearound, and aportion except for the overlap between the moved circle and the crosssection is defined as the central portion of the cell aggregate. At thistime, the cross section which gives largest cross-section area is mostpreferable. As to the center of the cell construct, with regard to thecross section which gives largest cross-section area, a radius Y isdetermined such that, when the center of a circle with the radius Y ismoved around the cross section along with the external margin of thecross section, the area of a portion except for the overlap between themoved circle and the cross section becomes one point. The center of acircle with the determined radius Y is moved therearound, and one pointexcept for the overlap between the moved circle and the cross section isdefined as the center of the cell construct. When the area does notbecome one point, and becomes a line segment, or when there are pluralsuch line segments, the middle point of each such line segment isdefined as the center.

The cell aggregate wherein the distance from the central portiondetermined as mentioned above to the outermost part of the cellconstruct is 10 μm or more, is considered as the cell aggregate of thepresent invention.

Specifically, the cell aggregate preferably has a region wherein theratio of the vascular cells in the central portion is 60% to 100%, morepreferably 65% to 100%, further preferably 80% to 100%, furtherpreferably 90% to 100%, to the whole areas of the vascular cells. Bloodvessel formation can be further promoted by adopting this range.

It is also preferred that the cell aggregate should have a region inwhich the density of the vascular cells in the central portion is1.0×10⁻⁴ cells/μm³ or more. It is more preferred that the whole centralportion of the cell aggregate should have the cell density describedabove. In this context, the phrase “have a region in which the densityis 1.0×10⁻⁴ cells/μm³ or more” specifically refers to that that there isa sample having the region with this density when section samples havinga thickness of 2 μm are prepared. The cell density is more preferably1.0×10⁻⁴ to 1.0×10⁻³ cells/μm³, further preferably 1.0×10⁻⁴ to 2.0×10⁻⁴cells/μm³, further preferably 1.1×10⁻⁴ to 1.8×10⁻⁴ cells/μm³, furtherpreferably 1.4×10⁻⁴ to 1.8×10⁻⁴ cells/μm³. Blood vessel formation can befurther promoted by adopting this range. It is preferred that the cellaggregate should satisfy both of the requirements (1) and (2).

Hereinafter, the present invention will be described more specificallywith reference to Examples. However, the present invention is notintended to be limited to Examples.

EXAMPLES Example 1 Recombinant Peptide

CBE3 described below was prepared as a recombinant peptide (described inWO2008-103041).

CBE3

Molecular weight: 51.6 kD

Structure: GAP[(GXY)63]3G

The number of amino acids: 571The number of RGD sequences: 12Imino acid content: 33%Substantially 100% of amino acids are derived from the GXY repeatstructures. The amino acid sequence of CBE3 does not contain any ofserine, threonine, asparagine, tyrosine, and cysteine. CBE3 has an ERGDsequence.Isoelectric point: 9.34, GRAVY value: −0.682, 1/IOB value: 0.323

Amino acid sequence (SEQ ID NO: 1 in the Sequence Listing) (same as SEQID NO: 3 in WO2008/103041 except that X at the end was modified to “P”)

GAP(GAPGLQGAPGLQGMPGERGAAGLPGPKGERGDAGPKGADGAPGAPGLQGMPGERGAAGLPGPKGERGDAGPKGADGAPGKDGVRGLAGPIGPPGERGAAGLPGPKGERGDAGPKGADGAPGKDGVRGLAGPIGPPGPAGAPGAPGLQGMPGERGAAGLPGPKGERGDAGPKGADGAPGKDGVRG LAGPP)3G

Example 2 Preparation of Recombinant Peptide Micro-Blocks

Amorphous micro-blocks were prepared as matrix blocks using therecombinant peptides CBE3. 1000 mg of the recombinant peptides wasdissolved in 9448 μL of ultrapure water. After addition of 152 μL of 1 NHCl, 400 μL of 25% glutaraldehyde was added thereto at a finalconcentration of 1.0% and reacted at 50° C. for 3 hours to prepare across-linked gelatin gel. This cross-linked gelatin gel was dipped in 1L of a 0.2 M glycine solution and shaken at 40° C. for 2 hours. Then,the cross-linked gelatin gel was shake-washed for 1 hour in 5 L ofultrapure water, and the ultrapure water was replaced by fresh one,followed by washing again for 1 hour. This procedure was repeated tocomplete a total of 6 washing operations. The cross-linked gelatin gelthus washed was frozen at −80° C. for 5 hours and then freeze-dried in afreeze dryer (EYELA, FDU-1000). The obtained freeze-dried product waspulverized with New Power Mill (Osaka Chemical Co., Ltd., New Power MillPM-2005). The pulverization was performed at the maximum number ofrevolutions for a total of 5 minutes (1 minute×5 runs). The obtainedparticles were sized through a stainless sieve to obtain 25 to 53 μm and53 to 106 μm recombinant peptide micro-blocks.

Example 3 Preparation of Natural Gelatin Micro-Blocks

Amorphous micro-blocks were prepared as matrix blocks using naturalgelatin (Nippi, Inc., Nippi gelatin/high grade gelatin APAT). 1000 mg ofthe natural gelatin was dissolved in 9448 μL of ultrapure water. Afteraddition of 152 μL of 1 N HCl, 400 μL of 25% glutaraldehyde was addedthereto at a final concentration of 1.0% and reacted at 50° C. for 3hours to prepare a cross-linked gelatin gel. This cross-linked gelatingel was dipped in 1 L of a 0.2 M glycine solution and shaken at 40° C.for 2 hours. Then, the cross-linked gelatin gel was shake-washed for 1hour in 5 L of ultrapure water, and the ultrapure water was replaced byfresh one, followed by washing again for 1 hour. This procedure wasrepeated to complete a total of 6 washing operations. The cross-linkedgelatin gel thus washed was frozen at −80° C. for 5 hours and thenfreeze-dried in a freeze dryer (EYELA, FDU-1000). The obtainedfreeze-dried product was pulverized with New Power Mill (Osaka ChemicalCo., Ltd., New Power Mill PM-2005). The pulverization was performed atthe maximum number of revolutions for a total of 5 minutes (1 minute×5runs). The obtained particles were sized through a stainless sieve toobtain 25 to 53 μm and 53 to 106 μm natural gelatin micro-blocks.

Example 4 Preparation of Mosaic Cell Mass Using Recombinant PeptideMicro-Blocks

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). After addition of recombinant peptide micro-blocks preparedin Example 2 to be 1.0 mg/mL, 100 μL of the mixture was inoculated to aSumilon Celltight X96U plate (Sumitomo Bakelite Co., Ltd., U-shapedbottom) and left standing for 18 hours to prepare a spherical mosaiccell mass of approximately 1 mm in diameter consisting of therecombinant peptide micro-blocks and the hMSC cells (0.002 μg of thepolymer blocks per cell). Then, the medium was replaced by achondrogenic differentiation medium (Takara Bio Inc.; hMSCDifferentiation BulletKit™, Chondrogenic, TGF-β3) (200 μL). At Day 7, aspherical mosaic cell mass of 1.54 mm in diameter (=thickness) wasformed (FIG. 1). In this context, this mosaic cell mass was prepared ina spherical shape because of being prepared in the U-shaped plate.Medium replacement was performed at Days 3, 7, 10, 14, 17, and 21.

Example 5 Preparation of Mosaic Cell Mass Using Natural GelatinMicro-Blocks

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). After addition of natural gelatin micro-blocks prepared inExample 3 to be 1.0 mg/mL, 100 μL of the mixture was inoculated to aSumilon Celltight X96U plate and left standing for 18 hours to prepare aspherical mosaic cell mass of approximately 1 mm in diameter consistingof the natural gelatin micro-blocks and the hMSC cells (0.002 μg of thepolymer blocks per cell). Then, the medium was replaced by achondrogenic differentiation medium (Takara Bio Inc.; hMSCDifferentiation BulletKit™, Chondrogenic, TGF-β3) (200 μL). At Day 7, aspherical mosaic cell mass of 1.34 mm in diameter (=thickness) wasformed (FIG. 2). In this context, this mosaic cell mass was prepared ina spherical shape because of being prepared in the U-shaped plate.

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). The natural gelatin micro-blocks prepared in Example 3 wereprepared by changing the conditions to final concentrations of 0.005mg/mL, 0.01 mg/mL, 0.1 mg/mL, 0.2 mg/mL, 1.0 mg/mL, and 2.0 mg/mL, 100μL of each mixture was inoculated to a Sumilon Celltight X96U plate andleft standing for 18 hours to successfully prepare spherical mosaic cellmasses of a little less than 1 mm in diameter (0.00001, 0.0002, 0.0004,0.002, and 0.004 μg of the polymer blocks per cell).

Example 6 Sample Analysis

A tissue slice was prepared for the mosaic cell mass prepared in Example4 using the recombinant peptide micro-blocks. After medium removal fromthe mosaic cell mass in the medium prepared in Example 4, the resultingmosaic cell mass was washed by the addition of 200 μL of PBS, and thisPBS was removed. This washing step was repeated twice. Then, the washedmosaic cell mass was dipped in 10% formalin, and formalin fixation wasperformed for 2 days. Then, the resulting cell mass was embedded inparaffin to prepare a tissue slice. The slice was stained with HE(hematoxylin-eosin), and the states of the cells and the gelatinmicro-blocks were analyzed. The results are shown in FIGS. 3, 4, and 5.It could thereby be confirmed that: a three-dimensional construct inwhich the gelatin micro-blocks and the cells were arranged in a mosaicpattern was prepared; and the cells were present in a normal state inthe mosaic cell mass. Moreover, from this cross-sectional slice, it wasshown that a mosaic cell mass of at least 720 μm or larger in thicknesscould be prepared.

Example 7 Fusion of Mosaic Cell Masses

Whether the mosaic cell masses prepared in Example 4 could be fused,i.e., whether the mosaic cell masses arranged were able to form a largerthree-dimensional construct by natural fusion, was examined. Two, three,or four mosaic cell masses of the 6th day prepared in Example 4 werearranged in a Sumilon Celltight X96U plate and cultured for 5 days. As aresult, it was revealed that the cells placed on the periphery of eachmosaic cell mass bound the mosaic cell masses to each other, whereby themosaic cell masses were naturally fused. FIG. 6 shows a photograph takenwith a stereoscopic microscope. Regarding the mosaic cell masses at thefusion start date (referred to as Day 6), the mosaic cell masses weremerely placed adjacently to each other. By contrast, at the 5th day fromthe start of fusion (referred to as Day 11), a new layer was formedbetween the mosaic cell masses, demonstrating the manner in which themosaic cell masses were fused. Also, FIGS. 7, 8, 9, 10, and 11 showresults of preparing a tissue slice of the fused mosaic cell masses andHE-staining the cross section thereof (fixation was performed using 10%formalin, and embedding was performed using paraffin embedding). As isevident from the drawings, a fusion layer was formed between the mosaiccell masses by the cells and extracellular matrices produced by thecells to fuse and bind the mosaic cell masses to each other. It wasthereby shown that the mosaic cell masses prepared in the presentinvention could be naturally fused and were able to form a largerconstruct by this fusion. Thus, it is demonstrated that use of thepresent invention achieves both of the preparation of a cell sheethaving a thickness and the preparation of a more stericthree-dimensional construct.

Example 8 Preparation of Mosaic Cell Mass Under Growth Medium UsingRecombinant Peptide Micro-Blocks

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). After addition of recombinant peptide micro-blocks preparedin Example 2 to be 1.0 mg/mL, 100 μL of the mixture was inoculated to aSumilon Celltight X96U plate and left standing for 18 hours to prepare aspherical mosaic cell mass of 1 mm in diameter (0.002 μg of the polymerblocks per cell). Then, the volume of the medium was increased to 200μL, and the mosaic cell mass was cultured with the medium replaced every3 days. At Day 7, a spherical mosaic cell mass of 1.34 mm in diameter(=thickness) was formed (in this context, this mosaic cell mass wasprepared in a spherical shape because of being prepared in the U-shapedplate). A photograph of a slice of the mosaic cell mass of Day 7 isshown in FIGS. 16 and 17. As is evident from the drawings, the thicknessof even a site with a small thickness reached at least 624 μm or largeron this cross-sectional slice.

Example 9 Increase in Volume of Mosaic Cell Mass (Under Growth Medium)

0.1 mg of the recombinant peptide micro-blocks prepared in Example 2 wassuspended in a growth medium (Takara Bio Inc.; MSCGM-CD™ BulletKit™) andadded during medium replacement to the mosaic cell mass of the 3rd day(Day 3) prepared in Example 8. Subsequently, 0.1 mg of the recombinantpeptide micro-blocks was added at the time of medium replacement at Days7, 10, 14, 17, and 21.

Time-dependent change in each of diameter (calculated as an average oftwo different diameters) in the observation of this mosaic cell massunder stereoscopic microscope, area of the photographed mosaic cellmass, and calculated volume (calculated according to 4/3πr³ from thediameter determined above) is shown in FIGS. 12, 13, 14, and 15. As aresult, a spherical mosaic cell mass of 3.41 mm in average diameter(=thickness) was finally formed at Day 21. It is thereby demonstratedthat a mosaic cell mass up to at least 3.41 mm in size can be prepared.It is also demonstrated that the size can be increased by continuingincrease in volume by this approach.

A tissue slice (HE-stained) at this time is shown in FIGS. 18 and 19. Asis evident from the drawings, the cells and the recombinant peptidemicro-blocks were arranged in a mosaic pattern. Moreover, since themosaic cell mass was approximately 3 mm in size and small as a sample,it was extremely difficult to correctly create a cross section throughthe center of the sphere. Thus, although the deepest portion of thesphere was not obtained in the slice, even a portion from which thisslice was collected in the sample was shown to be at least 1.17 mm inthickness.

As shown in FIGS. 12, 13, and 14, diameter was not changed in a mosaiccell mass cultured without adding the recombinant peptide micro-blocksduring medium replacement at Days 7, 10, 14, 17, and 21. In the mosaiccell mass cultured without adding the recombinant peptide micro-blocks,a layered structure consisting only of the cells and extracellularmatrices produced by the cells is formed by the proliferated cells inthe outermost layer of the mosaic cell mass. As a result, the state inwhich the diffusion of nutrition is blocked by the layer of the cellsand the produced extracellular matrices is formed to prevent the cellsfrom being further proliferated (sized up). This is the reason for nochange in diameter. On the other hand, when the recombinant peptidemicro-blocks are constantly added at the timing of medium replacement,these recombinant peptide micro-blocks are always fit in the mosaicpattern together with the proliferated cells, whereby the mosaicstructure consisting of the cells and the recombinant peptidemicro-blocks can continue to be maintained even after cellproliferation. As a result, the supply pathway of nutrition provided bythe recombinant peptide micro-blocks is always secured, and the outerlayer unintentionally formed by the cells and the produced extracellularmatrices is not generated. The resulting mosaic cell mass can be sizedup.

Example 10 Increase in Volume of Mosaic Cell Mass (Under ChondrogenicDifferentiation Medium)

0.1 mg of the recombinant peptide micro-blocks (0.1 mg) prepared inExample 2 was suspended in a chondrogenic differentiation medium (TakaraBio Inc.; hMSC Differentiation BulletKit™, Chondrogenic, TGF-β3) andadded during medium replacement to the mosaic cell mass of the 3rd day(Day 3) prepared in Example 4. Subsequently, 0.1 mg of the recombinantpeptide micro-blocks was added at the time of medium replacement at Days7, 10, 14, 17, and 21.

Time-dependent change in each of diameter (calculated as an average oftwo different diameters) in the observation of this mosaic cell massunder stereoscopic microscope, area of the photographed mosaic cellmass, and calculated volume (calculated according to 4/3πr³ from thediameter determined above) is shown in FIGS. 12, 13, 14, and 15. As aresult, a spherical mosaic cell mass of 2.05 mm in average diameter(=thickness) was finally formed at Day 21. It is thereby demonstratedthat a mosaic cell mass up to at least 2.05 mm in size can be prepared.It is also demonstrated that the size can be increased by continuingincrease in volume by this approach.

A tissue slice (HE-stained) at this time is shown in FIGS. 20 and 21. Asis evident from the drawings, the cells and the recombinant peptidemicro-blocks were arranged in a mosaic pattern. Moreover, since themosaic cell mass was approximately 2 mm in size and small as a sample,it was extremely difficult to correctly create a cross section throughthe center of the sphere. Thus, although the deepest portion of thesphere was not obtained in the slice, even a portion from which thisslice was collected in the sample was shown to be at least 897 μm inthickness.

As shown in FIGS. 12, 13, and 14, diameter was not changed in a mosaiccell mass cultured without adding the recombinant peptide micro-blocksduring medium replacement at Days 7, 10, 14, 17, and 21. In the mosaiccell mass cultured without adding the recombinant peptide micro-blocks,a layered structure consisting only of the cells and extracellularmatrices produced by the cells is formed by the proliferated cells inthe outermost layer of the mosaic cell mass. As a result, the state inwhich the diffusion of nutrition is blocked by the layer of the cellsand the produced extracellular matrices is formed to prevent the cellsfrom being further proliferated (sized up). This is the reason for nochange in diameter. On the other hand, when the recombinant peptidemicro-blocks are constantly added at the timing of medium replacement,these recombinant peptide micro-blocks are always fit in the mosaicpattern together with the proliferated cells, whereby the mosaicstructure consisting of the cells and the gelatin micro-blocks cancontinue to be maintained even after cell proliferation. As a result,the supply pathway of nutrition provided by the recombinant peptidemicro-blocks is always secured, and the outer layer unintentionallyformed by the cells and the produced extracellular matrices is notgenerated. The resulting mosaic cell mass can be sized up.

Example 11 Determination of Amount of GAG Produced in Mosaic Cell Mass(Time-Dependent Change)

The amount of glycosaminoglycan in each mosaic cell mass was determinedfor the mosaic cell masses prepared in Examples 4 and 5 (hMSCcells+recombinant peptide and hMSC cells+natural gelatin) and a cellmass prepared using only the cells (prepared by the same approach as inExample 4 without the gelatin blocks). Measurement was performed by amethod using a Dimetylmethylene blue dye (Farndale et al., Improvedquantitation and sulphated glycosaminoglycans by use ofdimethylmethylene blue. Biochimica et Biophysica Acta 883 (1986)173-177), and Sulfated GAG Quantification Kit (Seikagaku BiobusinessCorp.) was used as a reagent. Absorbance at 530 nm was measured forquantification. As shown in FIG. 21, it was confirmed thatcharacteristic absorption peaks were seen at 525-530 nm by the approach.

Results of determining the amount of GAG over time are shown in thegraph of FIG. 22. As a result, the amount of glycosaminoglycan (GAG)produced was low in the cell mass prepared without the gelatinmicro-blocks or the recombinant peptide micro-blocks, whereas the amountof GAG produced was exceedingly high in the mosaic cell mass preparedwith the natural gelatin micro-blocks and the mosaic cell mass preparedwith the recombinant peptide micro-blocks. It could thereby be confirmedthat: chondrogenic differentiation was promoted in the mosaic cellmasses prepared in Examples 4 and 5; and the prepared mosaic cell masseshad functions as cells (had the ability to produce GAG). Furthermore,the amount of GAG produced was significantly higher in the mosaic cellmass prepared with the recombinant peptide micro-blocks than the mosaiccell mass prepared with the natural gelatin micro-blocks. Thisdemonstrated that the mosaic cell mass prepared with the recombinantpeptide micro-blocks was able to maintain higher cell activity andsubstrate-producing activity than those brought about by the naturalgelatin micro-blocks, and showed that use of the recombinant peptide wasable to achieve the amount of the substrate produced, which wasimpossible to achieve with the natural gelatin.

Example 12 ATP Quantification for Mosaic Cell Mass

The amount of ATP (adenosine triphosphate) produced/retained by thecells in each mosaic cell mass was determined. ATP is known as an energysource for general organisms. The active metabolic state and activitystate of cells can be known by determining the amount of ATPsynthesized/retained. CellTiter-Glo (Promega Corp.) was used inmeasurement. For comparison, the amount of ATP in each mosaic cell masswas determined using CellTiter-Glo for the mosaic cell masses preparedin Examples 4 and 5 (hMSC cells+recombinant peptide and hMSCcells+natural gelatin) and a cell mass prepared using only the cells(prepared by the same approach as in Example 4 without the gelatinblocks), all of which were of Day 7.

The results are shown in FIG. 23. As is thereby evident, the amount ofATP produced/retained was significantly higher (p<0.01) in the mosaiccell mass prepared using the recombinant peptide micro-blocks or thegelatin micro-blocks than the cell mass prepared using only the cells.This suggests that the micro-blocks are fit in the mosaic pattern,whereby the nutrition supply pathway into the mosaic cell mass isprovided by the micro-blocks and the highly active metabolic state ofthe cells is more maintained than in the mass consisting only of thecells. It was further demonstrated that the amount of ATPproduced/retained was significantly higher in the mosaic cell massprepared with the recombinant peptide micro-blocks than the mosaic cellmass prepared with the natural gelatin micro-blocks. It was therebydemonstrated that the mosaic cell mass prepared with the recombinantpeptide micro-blocks exhibited higher cell survival than that broughtabout by the natural gelatin micro-blocks and the cells within thismosaic cell mass was alive. Use of the recombinant peptide was shown tobe able to achieve improvement in cell survival, which was impossible toachieve with the natural gelatin.

Example 13 Preparation of PLGA Micro-Blocks

0.3 g of PLGA (poly(lactic-co-glycolic acid); Wako Pure ChemicalIndustries, Ltd., PLGA7520) was dissolved in dichloromethane (3 mL). ThePLGA solution was vacuum dried in a dryer (EYELA, FDU-1000) to obtain adried product of PLGA. The dried product of PLGA was pulverized with NewPower Mill (Osaka Chemical Co., Ltd., New Power Mill PM-2005). Thepulverization was performed at the maximum number of revolutions for 10seconds×20 runs. The obtained particles were sized through a stainlesssieve to obtain 25 to 53 μm and 53 to 106 μm PLGA micro-blocks.

PLGA: “1/IOB” value: 0.0552

Example 14 Preparation of Mosaic Cell Mass Using PLGA

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). After addition of the PLGA micro-blocks prepared in Example13 (prepared by changing the conditions to final concentrations of 0.1mg/mL, 0.2 mg/mL, 1.0 mg/mL, and 2.0 mg/mL), 100 μL of each mixture wasinoculated to a Sumilon Celltight X96U plate and left standing for 18hours to prepare spherical mosaic cell masses of a little less than 1 mmin diameter (0.0002, 0.0004, 0.002, and 0.004 μg of the polymer blocksper cell). Then, the volume of the medium was increased to 200 μL, andeach mosaic cell mass was cultured with the medium replaced every 3days. In this context, this mosaic cell mass was prepared in a sphericalshape because of being prepared in the U-shaped plate. A stereoscopicmicroscope photograph of the PLGA mosaic cell mass of Day 2 is shown inFIG. 24.

Example 15 Preparation of Agarose Micro-Blocks

Ultrapure water (100 mL) was added to 5 g of agarose powders, and thepowders were dissolved by heating using a microwave oven. The obtained5% agarose solution was bought back to room temperature to obtain solidmatter. The solid matter was frozen at −80° C. for 5 hours and thenfreeze-dried in a freeze dryer (EYELA, FDU-1000) to obtain afreeze-dried product of agarose. The freeze-dried product of agarose waspulverized with New Power Mill (Osaka Chemical Co., Ltd., New Power MillPM-2005). The pulverization was performed at the maximum number ofrevolutions for 10 seconds×20 runs. The obtained particles were sizedthrough a stainless sieve to obtain 25 to 53 μm and 53 to 106 agarosemicro-blocks.

IOB value: 3.18

Example 16 Preparation of Mosaic Cell Mass Using Agarose

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 500,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGM-CD™BulletKit™). After addition of the agarose micro-blocks prepared inExample 15 (prepared by changing the conditions to final concentrationsof 0.1 mg/mL and 1.0 mg/mL), 100 μL of each mixture was inoculated to aSumilon Celltight X96U plate and left standing for 18 hours to preparespherical mosaic cell masses of a little less than 1 mm in diameter(0.0002 and 0.002 μg of the polymer blocks per cell). Then, the volumeof the medium was increased to 200 μL, and each mosaic cell mass wascultured with the medium replaced every 3 days. In this context, thismosaic cell mass was prepared in a spherical shape because of beingprepared in the U-shaped plate.

Example 17 Preparation of Mosaic Cell Mass Using Cardiac Muscle Cells

New-born SD rat cardiac muscle cells (rCMCs) were adjusted to 500,000cells/mL with a medium for cardiac muscle cells (Primary Cell Co., Ltd;CMCM culture medium for cardiac muscle cells). After addition ofrecombinant peptide micro-blocks prepared in Example 2 to be 0.5, 1.0 or3.0 mg/mL, 100 μL of each mixture was inoculated to a Sumilon CelltightX96U plate (Sumitomo Bakelite Co., Ltd., U-shaped bottom) and leftstanding for 18 hours to prepare mosaic cell masses of approximately 1to 2 mm in diameter consisting of the recombinant peptide micro-blocksand the rCMC cells (0.001, 0.002, and 0.006 μg of the polymer blocks percell). Medium replacement was performed at Days 3, 7, 10, 14, 17, and21.

At the stages of Days 1 and 3, the rCMC mosaic cell mass could alreadybe confirmed to beat in synchronization as the whole construct (FIG.25). Since moving images are difficult to show in the specification,FIG. 25 is an image taken by capturing still images of the same spotafter 0.2 seconds from the moving images. As is evident from the sitemarked with the triangle, the whole construct moved in two pictures.

This could show that even use of cardiac muscle cells was able to formthe three-dimensional cell construct (mosaic cell mass) of the presentinvention, and also demonstrated that the mosaic cell mass containingthe cardiac muscle cells was obtained as a cell construct that beat insynchronization as the whole construct.

Example 18 Preparation of Mosaic Cell Mass Using GFP-Expressing HUVECs(Human Umbilical Vein Endothelial Cells)

GFP-expressing human umbilical vein endothelial cells (GFP-HUVECs;Angio-Proteomie) were adjusted to 500,000 cells/mL with a medium forendothelial cells (Kurabo Industries Ltd.; Medium 200S, LSGS,antimicrobial agent GA solution). After addition of recombinant peptidemicro-blocks prepared in Example 2 to be 0.3, 1.0 or 3.0 mg/mL, 100 μLof each mixture was inoculated to a Sumilon Celltight X96U plate(Sumitomo Bakelite Co., Ltd., U-shaped bottom) (0.0006, 0.002, and 0.006μg of the polymer blocks per cell). Likewise, the cells were alsoadjusted to 1,500,000 cells/mL, and after addition of recombinantpeptide micro-blocks prepared in Example 2 to be 1.0 mg/mL, 100 μL or200 μL of the mixture was inoculated to a Sumilon Celltight X96U plate(Sumitomo Bakelite Co., Ltd., U-shaped bottom) and prepared. All of themwere separately left standing for 18 hours to prepare mosaic cell massesof approximately 1 to 2 mm in diameter consisting of the recombinantpeptide micro-blocks and the GFP-HUVEC cells. Medium replacement wasperformed at Days 3, 7, 10, 14, 17, and 21.

FIG. 26 shows microscope photographs and fluorescence microscopephotographs of a mosaic cell mass of 50,000 cells+0.03 mg of themicro-blocks and a mosaic cell mass of 300,000 cells+0.2 mg of themicro-blocks. Since the GFP-HUVEC cells emit the fluorescence of GFP,distribution in the mosaic cell mass is easily understood by means ofthe fluorescence microscope. Even use of vascular endothelial cells wasthereby shown to be able to prepare the three-dimensional cell construct(mosaic cell mass) of the present invention.

It was also demonstrated that the cell construct (mosaic cell mass) ofthe present invention could be formed with diverse cells, such asmesenchymal stem cells, cardiac muscle cells, and vascular endothelialcells. At the same time, it was shown that the cell construct (mosaiccell mass) of the present invention could be formed with diverse polymerblocks, such as recombinant peptide blocks, animal gelatin blocks, PLGAblocks, and agarose blocks. This proved that the three-dimensional cellconstruct (mosaic cell mass) of the present invention could be formedwith diverse cell species and diverse polymer block species.

Example 19-(1) Preparation of Mosaic Cell Mass Using Recombinant PeptideMicro-Blocks (hMSCs)

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 100,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGMBulletKit™). After addition of recombinant peptide micro-blocks preparedin Example 2 to be 0.1 mg/mL, 200 μL of the mixture was inoculated to aSumilon Celltight X96U plate (Sumitomo Bakelite Co., Ltd., U-shapedbottom), centrifuged (600 g, 5 minutes) with a tabletop platecentrifuge, and left standing for 24 hours to prepare a spherical mosaiccell mass of approximately 1 mm in diameter consisting of therecombinant peptide micro-blocks and the hMSC cells (0.001 μg of thepolymer blocks per cell). In this context, this mosaic cell mass wasprepared in a spherical shape because of being prepared in the U-shapedplate.

Example 19-(2) Larger Size by Fusion of Mosaic Cell Masses

Whether the mosaic cell masses prepared in Example 19-(1) could befused, i.e., whether the mosaic cell masses arranged were able to form alarger three-dimensional construct by natural fusion, was examined.First, a rectangular silicon sheet (3 mm thick) suitable for the size ofPrimeSurface 90 mm dish was prepared, and a piece of 1.5 cm square washollowed out of the central portion. The resulting silicon sheet wassterilized with ethanol, washed with PBS, and used. It was put inPrimeSurface 90 mm dish, and 1,500 mosaic cell masses prepared inExample 19-(1) were placed thereon, so that they were arranged in thesite of 1.5 cm square. 50 ml of a growth medium (Takara Bio Inc.; MSCGMBulletKit™) was gently added thereto, and the mosaic cell masses werecultured for 2 days. As a result, a fused form of the mosaic cell massesof 1.5 cm square and 2 mm in thickness could be prepared. FIG. 27 showsa photograph taken with a stereoscopic microscope. From a HE-stainedcross sectional slice of this fused form, it could also be confirmedthat the cells inside thereof survived. It was thereby shown that themosaic cell masses could be naturally fused and were able to form alarger construct of cm order by this fusion. Thus, it is demonstratedthat the mosaic cell mass can be prepared into a cell sheet having athickness as used in cell transplantation and can be prepared into amore steric three-dimensional construct.

Example 20 Preparation of Mosaic Cell Mass Using Recombinant PeptideMicro-Blocks (hMSCs+hECFCs) Example 20-(1)

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 100,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGMBulletKit™). After addition of recombinant peptide micro-blocks preparedin Example 2 to be 0.1 mg/mL, 200 μL of the mixture was inoculated to aSumilon Celltight X96U plate, centrifuged (600 g, 5 minutes) with atabletop plate centrifuge, and left standing for 24 hours to prepare aspherical mosaic cell mass of approximately 1 mm in diameter consistingof the recombinant peptide micro-blocks and the hMSC cells. Then, themedium was removed, and human vascular endothelial precursor cells(hECFCs) were adjusted to 100,000 cells/mL with a growth medium (Lonza;EGM-2+ECFC serum supplement). After addition of recombinant peptidemicro-blocks prepared in Example 2 to be 0.025 mg/mL, 200 μL of themixture with the mosaic cell mass containing the hMSC cells wasinoculated to the Sumilon Celltight X96U plate, centrifuged (600 g, 5minutes) with a tabletop plate centrifuge, and left standing for 24hours to prepare a mosaic cell mass in which a layer of hECFCs and therecombinant peptide micro-blocks was formed to surround the sphericalmosaic cell mass of approximately 1 mm in diameter consisting of therecombinant peptide micro-blocks and the hMSC cells. In this context,this mosaic cell mass was prepared in a spherical shape because of beingprepared in the U-shaped plate.

Example 20-(2)

Human vascular endothelial precursor cells (hECFCs) were adjusted to100,000 cells/mL with a growth medium (Lonza; EGM-2+ECFC serumsupplement). After addition of recombinant peptide micro-blocks preparedin Example 2 to be 0.05 mg/mL, 200 μL of the mixture was inoculated to aSumilon Celltight X96U plate, centrifuged (600 g, 5 minutes) with atabletop plate centrifuge, and left standing for 24 hours to prepare aflat mosaic cell mass consisting of ECFCs and the recombinant peptidemicro-blocks. Then, the medium was removed, and human bonemarrow-derived mesenchymal stem cells (hMSCs) were adjusted to 100,000cells/mL with a growth medium (Takara Bio Inc.; MSCGM BulletKit™). Afteraddition of recombinant peptide micro-blocks prepared in Example 2 to be0.1 mg/mL, 200 μL of the mixture with the hECFC mosaic cell mass wasinoculated to the Sumilon Celltight X96U plate, centrifuged (600 g, 5minutes) with a tabletop plate centrifuge, and left standing for 24hours to prepare a spherical mosaic cell mass of approximately 1 mm indiameter that consisted of the recombinant peptide micro-blocks and thehMSC cells and incorporated the mosaic cell mass consisting of ECFCs andthe recombinant peptide micro-blocks. In this context, this mosaic cellmass was prepared in a spherical shape because of being prepared in theU-shaped plate (the mosaic cell mass obtained here is designated as A).Furthermore, when the amounts of the human vascular endothelialprecursor cells (hECFCs) and the recombinant peptide micro-blocks werechanged to 200,000 cells/mL and 0.1 mg/mL, respectively, and the amountsof the human bone marrow-derived mesenchymal stem cells (hMSCs) and therecombinant peptide micro-blocks were changed to 200,000 cells/mL and0.2 mg/mL, respectively, a mosaic cell mass of approximately 1 mm inthickness and approximately 1.5 mm in diameter was also successfullyprepared (the mosaic cell mass obtained here is designated as B).

Example 20-(3)

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 100,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGMBulletKit™), and human vascular endothelial precursor cells (hECFCs)were adjusted to 100,000 cells/mL with a growth medium (Lonza;EGM-2+ECFC serum supplement). After addition of recombinant peptidemicro-blocks prepared in Example 2 to be 0.15 mg/mL, 200 μL of themixture was inoculated to a Sumilon Celltight X96U plate, centrifuged(600 g, 5 minutes) with a tabletop plate centrifuge, and left standingfor 48 hours to prepare a spherical mosaic cell mass of approximately 1mm in diameter consisting of the recombinant peptide micro-blocks,hMSCs, and hECFCs. In this context, this mosaic cell mass was preparedin a spherical shape because of being prepared in the U-shaped plate.

Comparative Example 1 Preparation of Cell Mass Using Only Cells (hMSCs)

Human bone marrow-derived mesenchymal stem cells (hMSCs) were adjustedto 375,000 cells/mL with a growth medium (Takara Bio Inc.; MSCGMBulletKit™). 200 μL thereof was inoculated to a Sumilon Celltight X96Uplate (Sumitomo Bakelite Co., Ltd., U-shaped bottom), centrifuged (600g, 5 minutes) with a tabletop plate centrifuge, and left standing for 24hours to prepare a spherical cell mass of approximately 1 mm in diameterconsisting of the hMSC cells. In this context, this mosaic cell mass wasprepared in a spherical shape because of being prepared in the U-shapedplate.

Comparative Example 2 Preparation of Cell Mass Using Only Cells(hMSCs+hECFCs)

Human vascular endothelial precursor cells (hECFCs) were adjusted to100,000 cells/mL with a growth medium (Lonza; EGM-2+ECFC serumsupplement). 200 μL thereof was inoculated to a Sumilon Celltight X96Uplate, centrifuged (600 g, 5 minutes) with a tabletop plate centrifuge,and left standing for 24 hours to prepare a hECFC cell mass. Then, themedium was removed, and human bone marrow-derived mesenchymal stem cells(hMSCs) were adjusted to 300,000 cells/mL with a growth medium (TakaraBio Inc.; MSCGM BulletKit™). 200 μL thereof with the hECFC mosaic cellmass was inoculated to the Sumilon Celltight X96U plate, centrifuged(600 g, 5 minutes) with a tabletop plate centrifuge, and left standingfor 24 hours to prepare a spherical cell mass of approximately 1 mm indiameter consisting of hECFCs and hMSCs (the cell mass obtained here isdesignated as A). Moreover, human vascular endothelial precursor cells(hECFCs) were adjusted to 200,000 cells/mL with a growth medium (Lonza;EGM-2+ECFC serum supplement). 200 μL thereof was inoculated to a SumilonCelltight X96U plate, centrifuged (600 g, 5 minutes) with a tabletopplate centrifuge, and left standing for 24 hours to prepare a hECFC cellmass. Then, the medium was removed, and human bone marrow-derivedmesenchymal stem cells (hMSCs) were adjusted to 200,000 cells/mL with agrowth medium (Takara Bio Inc.; MSCGM BulletKit™). 200 μL thereof withthe hECFC mosaic cell mass was inoculated to the Sumilon Celltight X96Uplate, centrifuged (600 g, 5 minutes) with a tabletop plate centrifuge,and left standing for 24 hours to prepare a spherical cell mass ofapproximately 1 mm in diameter consisting of hECFCs and hMSCs (the cellmass obtained here is designated as B).

Sample Analysis

A tissue slice was prepared for the mosaic cell masses prepared inExamples 19-(1) and 20 and Comparative Example 1 using the recombinantpeptide micro-blocks. The thickness of the slice was set to 2 μm. Aftermedium removal from each prepared mosaic cell mass in the medium, theresulting mosaic cell mass was washed by the addition of 200 μL of PBS,and this PBS was removed. This washing step was repeated twice. Then,the washed mosaic cell mass was dipped in 10% formalin, and formalinfixation was performed. Then, the resulting cell mass was embedded inparaffin to prepare a tissue slice. For Example 19-(1) and ComparativeExample 1, the slice was stained with HE (hematoxylin-eosin), and thestates of the cells and the recombinant peptide micro-blocks wereanalyzed. The results are shown in FIGS. 28 and 29. It could thereby beconfirmed that: a three-dimensional construct in which the recombinantpeptide micro-blocks and the cells were arranged in a mosaic pattern wasprepared in the mosaic cell mass; and the cells were present in a normalstate in the mosaic cell mass. Moreover, from this cross-sectionalslice, it was shown that a mosaic cell mass and a cell mass of at least500 μm in thickness could be prepared.

Furthermore, the slice of each mosaic cell mass of Example 20 wasimmunostained with an anti-CD31 antibody (EPT, Anti CD31/PECAM-1) forhECFC staining or with an anti-CD29 antibody (EPT, Anti Integrin β-1(CD29)) for hMSC/hECFC staining using a kit using DAB color development(Dako LSAB2 kit, Universal, K0673 Dako LSAB2 kit/HRP (DAB), for use withboth rabbit and mouse primary antibodies) (FIGS. 30, 31, 32, and 33).The ratio of the area of hECFCs (vascular cells) in the central portionwas determined for the mosaic cell masses prepared in Examples 20-(1) to20-(3) using the image processing software ImageJ described above andthe staining method using an anti-CD31 antibody. In this context, the“central portion” is as defined above.

As a result, the ratio of the area of hECFCs (vascular cells) in thecentral portion of the mosaic cell mass of Example 20-(1) was 24%; theratio of the area of hECFCs in the central portion of the mosaic cellmass of Example 20-(2) was 91% for both A and B; and the ratio of thearea of hECFCs in the central portion of the mosaic cell mass of Example20-(3) was 67%.

Furthermore, the density of the hECFC cells present in the centralportion was calculated for each mosaic cell mass of Example 20 bysuperimposing the anti-CD31 antibody staining image and the HE staining(hematoxylin-eosin staining) image. The density of the vascular cells inthe central portion can be determined by actually counting the number ofcells in a thin section sample and dividing the number of cells byvolume. First, these two images were superimposed using Photoshop, andthe number of anti-CD31 antibody-stained cell nuclei overlapping with HEstained cell nuclei was counted to calculate the number of cells.Meanwhile, the volume was determined by determining the area of thecentral portion using ImageJ and multiplying the area by 2 μm as thethickness of the thin section sample.

As a result, the number of the hECFC cells (vascular cells) in thecentral portion of the mosaic cell mass of Example 20-(1) was 1.58×10⁻⁵cells/μm³; the number of the hECFC cells in the central portion of themosaic cell mass A of Example 20-(2) was 1.12×10⁻⁴ cells/μm³; and thenumber of the hECFC cells in the central portion of the mosaic cell massof Example 20-(3) was 1.06×10⁻⁴ cells/μm³. In the case of B of Example20-(2) in which the number of cells and the weight of the blocks weredoubled, the number of the hECFC cells in the central portion was1.72×10⁻⁴ cells/μm³.

Example 21 In Vivo Survival Difference Evaluation Test in Mice UsinghMSC Mosaic Cell Mass

A test was conducted in vivo in mice to confirm that hMSCs at the centerof the mosaic cell mass survived.

Transplantation of Mosaic Cell Mass and Cell Mass

Five-week-old male Balb/c Nude mice (Charles River Laboratories Japan,Inc.) were raised for approximately 5 weeks and used in the test whenthey were approximately 10 weeks old. First, the skin between the firstand second ankle joints (hereinafter, this region is referred to as thelower leg) from the edge of the limb of each mouse was incised underanesthesia with scissors and opened up. Then, the muscle in the lowerleg was incised by approximately 5 mm with a knife, and the hMSC mosaiccell mass prepared in Example 19-(1) or the hMSC cell mass prepared inComparative Example 1 was implanted in the incision site using tweezers.The incision site in the muscle was sutured with suture thread, and theskin was further sutured.

In addition, a transplantation method involving muscular injection intothe lower leg was also performed as another approach. Ten hMSC mosaiccell masses prepared in Example 19-(1) or ten hMSC cell masses preparedin Comparative Example 1 were placed together with 200 μl of a hMSCgrowth medium (Takara Bio Inc.; MSCGM BulletKit™) in a 1-mm syringe andinjected to the muscle in the lower leg using a 18 G injection needle(Terumo Corp.).

Collection of Mosaic Cell Mass

Anatomy was performed 2 days, 5 days, 8 days, and 13 days aftertransplantation. In the case of the transplantation by muscle incision,the skin in the lower leg of each mouse was taken off, and the suturethread in the muscle in the lower leg was removed. The incision site wasopened with a knife. After visual confirmation of the transplanted hMSCmosaic cell mass and hMSC cell mass, the femoral region together withbone was cut with scissors and further cut off at the ankle.

In the case of the transplantation by muscular injection, the skin inthe lower leg of each mouse was taken off, and the muscle in the lowerleg was incised with a knife. After visual confirmation of thetransplanted hMSC mosaic cell mass and hMSC cell mass, the muscle towhich each cell mass was attached was cut out.

Sample Analysis

A tissue slice was prepared for the lower leg containing the mosaic cellmass or the cell mass, the muscle to which the hMSC mosaic cell mass orthe hMSC cell mass was attached, and the mosaic cell mass and cell massbefore transplantation. The femoral region was dipped in 4%paraformaldehyde, and formalin fixation was performed. Then, theresulting product was embedded in paraffin to prepare a tissue slice ofthe lower leg containing the hMSC mosaic cell mass or the hMSC cellmass. The slice was stained with HE (hematoxylin-eosin) andimmunostained with an anti-CD29 antibody for hMSC cell staining using aDAB color development method to analyze cell distribution. An image ofthe HE-stained slice at the 5th day after transplantation is shown(FIGS. 34 and 35).

Referring to FIG. 34, the nuclei of the hMSC cells at the center of themosaic cell mass were clearly shown, and 100% of hMSCs in the wholemosaic cell mass survived. By contrast, referring to FIG. 35, nuclearpyknosis and obscuration occurred at the center of the mass consistingonly of the cells, and the hMSC cells necrotized while 62.7% cellssurvived in the whole cell mass. It could be confirmed that hMSCsnecrotized at the center of the hMSC cell mass in vivo, whereas hMSCswere able to survive even at the center of the hMSC mosaic cell mass.

Moreover, it could be confirmed that blood vessels were formed withinthe hMSC mosaic cell mass at the 5th day. The number of blood vesselswas 6 per area. By contrast, no blood vessel formation was seen withinthe hMSC cell mass, and the number of blood vessels per area was 0. ThehMSC mosaic cell mass was shown to form blood vessels therewithin invivo and create an environment suitable for cell survival.

Example 22-(1) In Vivo Blood Vessel Formation Difference Evaluation Testin Mice Using Mosaic Cell Mass of hMSCs and hECFCs Transplantation ofMosaic Cell Mass

Four-week-old male NOD/SCID mice (Charles River Laboratories Japan,Inc.) were raised for approximately 8 weeks and used in the test whenthey were approximately 12 weeks old. The abdominal hair of each mousewas removed under anesthesia. The upper abdominal region wassubcutaneously slit up, and scissors were inserted through the slit totake off the skin from the muscle. Then, each of 3 types of hMSC+hECFCmosaic cell masses prepared in Examples 20(1) to 20(3) was scooped withtweezers and subcutaneously transplanted in the abdominal region 1.5 cmbelow the slit, and the slit in the skin was sutured.

Collection of Mosaic Cell Mass

Anatomy was performed 5 days, 14 days, and 28 days aftertransplantation. The skin in the abdominal region was taken off, and theskin to which each mosaic cell mass was attached was cut into a squareof approximately 1 cm² in size. In the case where the mosaic cell masswas also attached to the muscle in the abdominal region, the mosaic cellmass was collected together with the muscle.

A tissue slice was prepared for the skin slice to which the mosaic cellmass was attached and the mosaic cell masses before transplantation. Theskin was dipped in 4% paraformaldehyde, and formalin fixation wasperformed. Then, the resulting product was embedded in paraffin toprepare a tissue slice of the skin containing each mosaic cell mass. Theslice was stained with HE (hematoxylin-eosin) and immunostained with ananti-CD31 antibody for hECFC staining using a DAB color developmentmethod to analyze blood vessel formation and the states of hMSC andhECFC behaviors within the mosaic cell mass. An image of the HE-stainedslice at the 5th day after transplantation is shown.

FIG. 36 is an image of the HE-stained slice using the mosaic cell massproduced in Example 20-(1). FIG. 37 is an image of the HE-stained sliceusing the mosaic cell mass produced in Example 20-(2). FIG. 38 is animage of the HE-stained slice using the mosaic cell mass produced inExample 20-(3). As is evident from all the images, blood vessels wereformed within the mosaic cell mass at the 5th day after transplantation.The formation of blood vessels in larger amounts was seen in the mosaiccell mass A produced in Example 20-(2), the mosaic cell mass produced inExample 20-(3), and the mosaic cell mass produced in Example 20-(1) inthis order, demonstrating that in vivo cell survival in the centralportion of the mosaic cell mass was evidently more favorable than thatof the cell mass. It was also demonstrated that: the mosaic cell masswas able to form blood vessels therewithin; and the ability to formblood vessels was rendered higher by particularly allowing hECFCs toexist therewithin.

Example 22-(2) In Vivo Blood Vessel Formation Difference Evaluation Testin Mice Using Mosaic Cell Mass of hMSCs and hECFCs Transplantation ofMosaic Cell Mass

Four-week-old male NOD/SCID mice (Charles River Laboratories Japan,Inc.) were used. The abdominal hair of each mouse was removed underanesthesia. The upper abdominal region was subcutaneously slit up, andscissors were inserted through the slit to take off the skin from themuscle. Then, each of 2 patterns of hMSC+hECFC mosaic cell masses (A andB) prepared in Examples 20(2) and 2 patterns of hMSC+hECFC cell masses(A and B) of Comparative Example 2 was scooped with tweezers andsubcutaneously transplanted in the later abdominal region 1.5 cm belowthe slit, and the slit in the skin was sutured.

Collection of Mosaic Cell Mass

Anatomy was performed 6 days, 14 days, and 28 days aftertransplantation. The skin in the abdominal region was taken off, and theskin to which each mosaic cell mass was attached was cut into a squareof approximately 1 cm² in size. In the case where the mosaic cell masswas also attached to the muscle in the abdominal region, the mosaic cellmass was collected together with the muscle.

A tissue slice was prepared for the skin slice to which the mosaic cellmass was attached and the mosaic cell masses before transplantation. Theskin was dipped in 4% paraformaldehyde, and formalin fixation wasperformed. Then, the resulting product was embedded in paraffin toprepare a tissue slice of the skin containing each mosaic cell mass. Theslice was stained with HE (hematoxylin-eosin) and immunostained with ananti-CD31 antibody for hECFC staining using a DAB color developmentmethod to analyze blood vessel formation and the states of hMSC andhECFC behaviors within the mosaic cell mass. An image of the HE-stainedslice at the 14th day after transplantation is shown.

FIG. 39 is an image of the HE-stained slice using the mosaic cell mass Aof Example 20-(2). FIG. 40 is an image of the HE-stained slice using themosaic cell mass B of Example 20-(2). As is evident from all the images,blood vessels were formed within the mosaic cell mass at the 14th dayafter transplantation. The formation of blood vessels in larger amountswas seen in the mosaic cell mass B of Example 20-(2) than the mosaiccell mass A of Example 20-(2). It was demonstrated that the ability toform blood vessels was rendered higher by allowing hECFCs to existwithin the mosaic cell mass and further increasing the number of hECFCs.On the other hand, FIG. 41 is an image of the HE-stained slice using thecell mass B of Comparative Example 2. The cell mass A of ComparativeExample 2 failed to be collected at the 14th day after transplantation.By contrast, the cell mass B of Comparative Example 2 became small, andno blood vessel was seen therein while cell death was also observed. Itcould thereby be confirmed that the cell mass without the blocks failedto form blood vessels and exhibited cell death even though it containedhECFCs.

1-19. (canceled)
 20. A method for transplanting cells, which comprisestransplanting a cell construct for cell transplantation which comprisespolymer blocks of biodegradable material and cells of at least one type,wherein the plural polymer blocks are arranged in spaces between theplural cells, wherein the polymer blocks each have a size from 1 μm to700 μm, the polymer blocks have surface irregularities obtained bypulverizing freeze-dried product which comprises the polymer, and thecells are isolated cells which were grown in vitro.
 21. The method fortransplanting cells according to claim 20, wherein the polymer havingbiocompatibility is polypeptide, polylactic acid, polyglycolic acid,PLGA, hyaluronic acid, glycosaminoglycan, proteoglycan, chondroitin,cellulose, agarose, carboxymethylcellulose, chitin, or chitosan.
 22. Themethod for transplanting cells according to claim 20, wherein thepolymer having biocompatibility is a recombinant peptide.
 23. The methodfor transplanting cells according to claim 20, wherein the polymerhaving biocompatibility has two or more cell adhesion signals in amolecule.
 24. The method for transplanting cells according to claim 22,wherein the recombinant peptide is represented by the formula:A-[(Gly-X-Y)_(n)]_(m)-B, wherein A represents any amino acid or aminoacid sequence; B represents any amino acid or amino acid sequence; eachX of total n independently represents any amino acid; each Y of total nindependently represents any amino acid; n represents an integer of 3 to100; m represents an integer of 2 to 10; and each Gly-X-Y of total n maybe the same as or different from each other.
 25. The method fortransplanting cells according to claim 22, wherein the recombinantpeptide has (1) the amino acid sequence represented by SEQ ID NO: 1, or(2) an amino acid sequence having 80% or higher homology to the aminoacid sequence represented by SEQ ID NO: 1 and having biocompatibility.26. The method for transplanting cells according to claim 20, whereinthe cell construct further comprises an angiogenesis factor.
 27. Themethod for transplanting cells according to claim 20, wherein the cellsare cells selected from the group consisting of pluripotent cells,somatic stem cells, precursor cells, and mature cells.
 28. The methodfor transplanting cells according to claim 27, wherein the cellscomprise non-vascular cells.
 29. The method for transplanting cellsaccording to claim 28, wherein the cells are only non-vascular cells.30. The method for transplanting cells according to claim 28, whereinthe cells are of two or more types comprising both non-vascular cellsand vascular cells.
 31. The method for transplanting cells according toclaim 30, wherein the cell construct has a region wherein the area ofthe vascular cells in the central portion of the cell construct islarger than the area of the vascular cells in the peripheral portion,wherein the central portion of the cell construct refers to an areacorresponding to a distance up to 80% from the center in the distancefrom the center to the surface of the cell construct, and the peripheralportion of the cell construct refers to an area from the position of 80%from the center to the surface of the construct.
 32. The method fortransplanting cells according to claim 31, wherein the cell constructhas a region wherein the ratio of the vascular cells in the centralportion is 60% to 100% to the whole vascular cells in the implant. 33.The method for transplanting cells according to claim 30, wherein thecell construct has a region wherein the density of the vascular cells inthe central portion is 1.0×10⁻⁴ cells/μm³ or more.